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The White House, facing fierce criticism from the gun lobby, has delayed approval of a proposed rule that federal law enforcement officials say could help them stanch the flow of U.S. assault rifles and other high-powered weapons to Mexico’s drug cartels.

The proposed rule, announced by Alcohol, Tobacco and Firearms acting director Kenneth Melson on Dec. 20,  would require U.S. firearms dealers in four southwest border states to report multiple sales of long guns, such as semi-automatic assault rifles which are frequently purchased by so-called “straw buyers” for the cartels. Melson had said he expected the proposed “emergency rule” would receive approval in early January 2011.

But the announced deadline date for White House approval, Jan. 5, has come and gone, leaving ATF officials bewildered and keenly disappointed. Some officials had expressed hopes  that President Barack Obama might even address the issue during his State of the Union speech Tuesday night as a positive step the administration was taking to address the issue of gun violence.

Instead, Obama failed to discuss guns in his speech, and now some ATF officials are wondering whether the proposed emergency rule will take effect at all.  One official with knowledge of the issue said the delay may relate to questions raised by critics about ATF's legal authority to issue such a proposed rule on an emergency basis.

“This is hugely demoralizing and embarrassing for ATF,” said one former agency official who has followed the debate over the rule closely, speaking on condition of anonymity.

U.S.: Gun raids show cartels at work in Ariz.

Reid Cherlin, a White House spokesman said the proposed rule is still “under review” by the Office of Management and Budget and declined to offer any guidance on when it might take effect, if at all. An ATF spokesman declined comment.

U.S. law enforcement officials said the need for the rule was dramatically highlighted this week by federal indictments in Arizona alleging that networks of “straw buyers” – many of them working for the Sinoloa Cartel and other Mexican drug trafficking organizations -- had illegally bought hundreds of firearms from U.S. gun stores. Out of 700 firearms allegedly illegally purchased by one network between September 2009 and December 2010, more than 640 were bought at a single gun store, the Lone Wolf Trading Co., in Glendale, Ariz., according to one indictment.  Most of the weapons were AK-47s, purchased in bulk quantities of 20 to 40, often by the same buyer within days of a previous purchase. In each case, the buyers filled out federal firearms affirming they were buying the guns for themselves and underwent standard federal background checks.  In fact, according  to  federal authorities, they were buying the guns in order to smuggle them to Mexico, where many were later recovered from drug cartel operatives.

 ATF officials say the proposed rule would be an invaluable “intelligence” tool that would allow them to at least identify suspicious activity at gun stores along the southwest border. Currently, firearms dealers such as Lone Wolf Trading are required to report to ATF whenever somebody buys two or more handguns within a five day period. But they are not required to file such reports in the case of long guns, such as AK-47s, even though such assault rifles are now the “weapons of choice” for the Mexican cartels, officials say.  In this case, the Lone Wolf gun store “did nothing wrong” by selling the AK-47s in bulk quantities, although from a law enforcement perspective, the multiple purchases "kind of hit you on the smell test,” said one U.S. law enforcement official, also speaking on condition of anonymity. 

The proposed rule has drawn strong e criticism from the National Rifle Association and gun industry groups, which have publicly urged members and supporters to file public comments expressing opposition to the White House Office of Management and Budget. (OMB, an arm of the White House executive office, must sign off on all proposed federal rules.)

Larry Keane, senior vice president of the National Shooting Sports Foundation, which represents the gun industry, said his group believes the proposed rule “won't assist law enforcement” and “will make it harder for firearms dealers to cooperate with ATF.”

“The cartels that are using straw purchasers will simply modify their behavior,” he said. “Instead of sending one purchaser to buy five firearms, they’ll send straw purchasers  to five different stores — or they’ll simply recruit five straw purchasers to buy one gun at a time.”

In addition, Keane said, “If ATF can ask for  this in these four states, they can ask for that nationwide and there’s no piece of information they can’t ask for.” 

The uncertainty about the rule has fueled the disappointment of gun control groups that Obama has failed to take any action to press for tighter gun control measures, even after the recent shooting rampage in Tucson that seriously wounded Rep. Gabrielle Giffords of Arizona. Many gun control advocates, such as New York Mayor Michael Bloomberg, had called on Obama to seize the opportunity to forcefully address the issue Tuesday night, pointing out that the president during the 2008 campaign had backed tougher measures, including reinstatement of the federal assault weapons ban.

Obama’s failure to say anything on the subject drew criticism from Bloomberg and other gun control advocates Wednesday.

“It’s depressing, but not surprising,” said Kristen Rand, legislative director of the Violence Policy Center, a group that advocates for gun control.

Responding to the criticism, White House Press Secretary Robert Gibbs suggested Wednesday that Obama may address the gun issue in the future. 

"I wouldn't rule out that at some point the president talks about the issues surrounding gun violence," Press Secretary Gibbs said aboard Air Force One on the way to an event with Obama in Wisconsin, according to the Washington Post. “I don't have a timetable or, obviously, what he would say."

More reporting by Michael Isikoff

By Michael Isikoff
NBC News National Investigative Correspondent

Now that Dick Cheney has opened the door to tighter gun restrictions, will President Barack Obama do the same?

That politically dicey question is playing out behind the scenes in the run-up to next week’s State of the Union. In the aftermath of the Tucson shooting of Rep. Gabrielle Giffords and federal Judge John Roll, gun control groups and some Democratic members of Congress are pushing to get the president to directly address the issue of gun violence in his speech to Congress next Tuesday, according to gun control advocates and congressional aides, who asked for anonymity.

Some Democratic party donors are also being urged to weigh in as part of a quiet lobbying effort to prod the president to finally speak out on an issue that he has studiously avoided since taking office, the advocates say.

“There’s a major push to get [Obama] to say something on this,” said Chad Ramsey, legislative director of the Brady Center to Prevent Gun Violence, a leading gun control group. “We’ve been told he will say something, but we’re not sure how strong it will be.”

There have been a number of different gun control ideas put forward since the Jan. 8 Tucson shooting. But gun control groups most of all want Obama’s endorsement of the bill introduced this week by Democratic Rep. Carolyn McCarthy of New York (with more than 40 co-sponsors so far). That bill would ban the sale or transfer of high-capacity gun magazines such as the one allegedly used by Jared L. Loughner to fire off more than 30 rounds. So far, the proposal (and a companion bill to be introduced next week by Democratic Sen. Frank Lautenberg of New Jersey) has yet to pick up a single Republican co-sponsor.

But backers were buoyed Wednesday when former vice president Dick Cheney, long a stalwart supporter of gun rights, appeared open to the idea, telling NBC’s Jamie Gangel in an interview, “maybe it's appropriate to re-establish that kind of thing.” (See the video of Cheney below.)

A White House official said that aides won't publicly comment on what Obama might or might not say in the Jan. 25 State of the Union. Asked specifically about the McCarthy-Lautenberg proposal to ban high-capacity magazines, Reid Cherlin, a White House press spokesman, said in an e-mail: “A number of proposals have been put forward in the days since these tragic shootings, and we’re going to be taking a close look at all of them.”

As a sign of just how tough a fight this issue would be, the National Rifle Association on Wednesday sent a letter to members of Congress criticizing "anti-gun activists" for pushing several "schemes" after Tucson. Referring specifically to the McCarthy-Lautenberg proposal to ban clips of more than 10 rounds, Chris Cox, the group's chief lobbyist, wrote: "These magazines are standard equipment for self-defense handguns and other firearms owned by tens of millions of Americans. Law-abiding private citizens choose them for many reasons, including the same reason police officers do: to improve their odds in defensive situations." (The NRA did not respond to a request to comment on Cheney's remarks to NBC.)

Until now, the entire subject of guns has been anathema at the White House. Obama during his 2008 campaign had pledged to push to reinstate the ban on semi-automatic assault weapons. The ban, which was enacted under President Clinton in 1994 and which lapsed under President Bush 10 years later, had included a provision that prohibited the manufacture of high-capacity detachable magazines.

But White House officials pretty much dropped the issue after Obama took office, going so far as to remove the campaign pledge from the White House website. Obama, who stopped talking about guns entirely, also waited nearly two years before nominating a director of the Bureau of Alcohol, Tobacco and Firearms, fearing that any candidate it sent up to the Senate would incur the wrath of the formidable National Rifle Association, according to administration sources. (Sure enough, its nominee, Andrew Traver, the ATF special agent in charge in Chicago, is the target of an NRA lobbying campaign. It remains far from clear he will ever get confirmed.)

Still, advocates say that the Tucson shooting was such a searing national tragedy that it may now be impossible for Obama to duck the subject. According to gun control groups, and some law enforcement officials, a ban on high-capacity magazines is the one specific proposal that might have made a difference in Tucson, at least in lowering the body count of six killed and 13 wounded. Because of the high-capacity magazine he had attached to his Glock 19 semi-automatic, Loughner was able to get off 31 or 32 shots before he had to reload. It was only when he did so that he was wrestled to the ground.

One prong of the gun control lobbying campaign is to try to line up law enforcement backing for the McCarthy proposal, starting with the Justice Department. Thanks to the intervention of a plugged-in donor, the group has secured a meeting on Jan. 25 with Attorney General Eric Holder — the same day as the State of the Union. (Holder is on record as supporting the assault weapons ban, but like other administration officials rarely talks about it anymore. ) The groups are also hoping that McCarthy may yet have some pull with her former chief of staff, Jim Messina, now the deputy White House chief of staff and one of Obama’s most influential aides. A McCarthy spokesman said that the congresswoman has been attempting to raise the subject of the magazine ban with Messina, but said he didn’t believe the two had spoken yet.)

But skeptics wonder how far the Messina connection will get the gun control advocates. One former senior law enforcement official who follows the gun issue closely, and who asked for anonymity, noted that after Messina worked for McCarthy he served as chief of staff to Democratic Sen. Max Baucus of Montana, a strong gun rights advocate. And Messina at times has served as a White House conduit to the NRA, the former official said.

In any case, this former official predicted that, for all the outside pressure it has been getting, the White House in the end will avoid the subject, concluding it's simply not worth taking on the NRA and that it's likely to lose in the end. “As a matter of political strategy, it would be as bad for him take this on as health care was,” said this former official. “It would become a distraction from everything else.”