A US Senate panel voted along party lines Tuesday to approve a Democratic bill requiring universal background checks for firearm sales, but passage through the full Congress will be more problematic.

The Senate Judiciary Committee voted 10-8 for the bill, which would close a loophole that allows unchecked sales at gun shows and on the Internet.

If passed, the measure -- seen as a key element of President Barack Obama's push to reduce weapons violence -- would result in the most substantial change to US gun legislation in a generation.

The White House hailed the background checks bill and a related school safety bill as "important measures that will help save lives."

"We look forward to continuing to work with Congress on this and on the other important pieces of legislation that are part of the president's comprehensive plan to reduce gun violence," White House spokesman Jay Carney told reporters after the committee vote.

But even the bill's main sponsor, Democrat Chuck Schumer, acknowledged it will be difficult to win passage in the full Senate and that lawmakers from both sides could clutter it with amendments.

"The issue of background checks remains the sweet spot," Schumer said in a statement.

"We will work nonstop in the next couple weeks to continue negotiating a bipartisan compromise."

The White House and Congress have zeroed in on potential measures to reduce gun violence in the wake of the December 14 massacre in Newtown, Connecticut, where a gunman slaughtered 20 children and six adults at an elementary school.

The committee also approved a gun-trafficking bill last week that toughens penalties for "straw purchasers" -- people who buy guns for others who are not allowed to own weapons -- and signed off on a measure Tuesday that would boost funding for school security.

But it put off until Thursday a vote on the most controversial of four measures: a revamped version of an assault weapons ban that was allowed to lapse in 2004.

The ban and universal background checks are opposed by most Republicans, and Democrats have struggled to find any Republicans willing to sign on.

"Mass shootings would continue to occur despite universal background checks, criminals will continue to steal guns and buy them illegally to circumvent the requirement," Republican Senator Chuck Grassley said.

"When that happens we will be back again debating whether gun registration's needed, and when registration fails, the next move will be gun confiscation," he said.

Schumer insisted the bill "explicitly says there is no registration, the bill explicitly says there is no confiscation."

Despite weeks of negotiations, he has yet to reach a compromise with Republicans -- or win over reluctant moderate Democrats in pro-gun states, like Senator Joe Manchin of West Virginia.

But Manchin said he was "still working" on a compromise that would settle the contentious issue of what to do with records from private gun sales. Licensed gun dealers are already required to keep sales documentation.

Manchin was part of a Senate Democrat luncheon Tuesday attended by the president, and the senator said Obama touched on the background check legislation, calling it "very important."

The bill would need 60 votes to overcome Republican obstruction in the 100-seat Senate. Democrats hold 55 seats so they would need at least five Republicans to go along.

It would then face an even tougher road in the Republican-held House, where several members openly oppose universal background checks.