A US Senate panel approved legislation Thursday that makes gun trafficking a federal crime, but bills banning assault weapons and expanding background checks to nearly all gun buyers face a tougher battle.

President Barack Obama applauded the vote by the Judiciary Committee in support of a bill that cracks down on "straw purchasers," who buy firearms for gang members and other criminals, saying he hoped to see it on his desk.

"I urge the Senate to give that bill a vote," he said. "I urge the House to follow suit."

The president has made it a priority to rein in gun violence in the aftermath of the mass shooting in Newtown, Connecticut where a gunman killed 20 children and six adults with a semi-automatic rifle last December.

A cornerstone of his effort has been an expansion of background checks, but lawmakers have been grappling with how to shepherd it through a divided Congress.

Senate Judiciary chairman Patrick Leahy said he hoped to move three more bills through committee in the coming week.

But the bill on federal background checks for all gun purchases hit a roadblock after two senators negotiating on its provisions brought their talks to a halt.

Democrat Chuck Schumer was seeking to team with Senator Tom Coburn, a Republican with an "A" rating from the National Rifle Association, but the pair failed to resolve a dispute over requiring that records of private gun sales be kept by the seller.

Republicans argue that such data should be destroyed, or it could ultimately be used to compile a national gun registry, something currently prohibited by law.

Despite the setback, Coburn insisted he was "still hopeful we'll get a bill that will actually enhance background checks."

"Our deal is to find the sweet spot in the middle," he told reporters.

Democrat Joe Manchin, of largely pro-gun West Virginia, said he remained optimistic about a bill that would close the "gun-show loophole," which allows private individuals to sell weapons to the public at gun shows or online without conducting a background check.

"Me and Tom Coburn and other Republicans, Mark Kirk, we're still working very feverishly," Manchin told AFP.

But debate at the Judiciary meeting hinted at difficulties ahead.

Senator Dianne Feinstein, who introduced a beefed up version of an assault weapons ban that expired in 2004, admitted she had "a very hard road" to get her bill through.

She said Republicans were deriding her ban, which would prohibit 157 assault weapons outright and ban high-capacity clips or magazines, as "some kind of wild-eyed scheme.

"It is not. The majority of people favor this legislation," she said, citing various polls.

Republican Chuck Grassley countered that such moves would be doubling down on a "failed strategy."

"Restrictions on gun rights of law abiding citizens do not work," he said.