US Democrats demanded a renewed gun debate Tuesday following the Washington Navy Yard shooting but admitted there was not enough support yet for new legislation.

The killing of 12 people by a gunman at the Washington base was greeted with a chorus of revulsion across the political spectrum.

But it will take more than rhetorical appeals for action to sway lawmakers, as this year's failed Senate effort to toughen gun control measures has already shown.

Senate Majority Leader Harry Reid said he wanted to revive the debate sooner rather than later, given the shooting at a Navy facility barely 1.5 miles (2.4 kilometers) from the US Capitol.

"But we've got to have the votes first. We don't have the votes," Reid told reporters after meeting with fellow Democrats.

"I hope we get them but we don't have them now."

The blunt assessment by the man who schedules floor debate in the Senate speaks volumes about the uphill battle facing gun control advocates.

President Barack Obama reacted furiously earlier this year after efforts to tighten gun control laws following December's massacre at Sandy Hook Elementary School foundered in Congress.

Several Democrats, including Senator Richard Blumenthal of Connecticut, said they hoped to reintroduce legislation including a measure that would expand background checks and ensure the mentally ill would not have access to firearms.

"I think there is a potential opening for a new consensus and new momentum and impetus for gun violence prevention," Blumenthal told AFP, but he acknowledged it would be a hard sell to Republicans, most of whom voted against the background check bill in April.

That bill failed by five votes in the 100-seat Senate (Reid changed his vote to "no" so he could bring up the legislation again), and it would have been an even tougher political lift in the Republican-controlled House of Representatives.

Connecticut's other US Senator, Chris Murphy, challenged his fellow lawmakers, saying they "can not continue to ignore this continuing slaughter."

"People are just not going to accept that Congress continues to sit on its hands while these mass shootings happen," he said, noting that more than 8,000 people have been killed by US gun violence in the nine months since Sandy Hook.

Republican Senator Bob Corker said he did not foresee action on guns this year.

"I bet that doesn't happen," he told AFP. "Nobody is talking to me about (gun reform). I've heard no discussions."

Asked if he has sensed any shift toward support of gun control in the aftermath of the Navy Yard shooting, Senator Tom Carper said "I don't think so."

Carper, a Democrat, chairs the Senate Homeland Security Committee, which he said may soon hold hearings on security shortcomings that may have led to a mentally unstable contractor gaining legitimate access to a military base.

The suspect in Monday's shooting, 34-year-old Aaron Alexis, was working on a Navy contract through computer giant Hewlett-Packard, but reports show he had prior run-ins with police.

"Whoever did the background check, were they aware of the earlier arrests, the charges?" Carper asked.

"I'm not sure that they were. So we're going to drill down on this."

Lawmakers including Senator John McCain, one of a handful of Republicans who voted for the background bill this year, said mental health could emerge as a focal point of legislation.

"It's an ongoing tragedy," McCain said of Monday's violence.

"But it also should focus our attention on people that show mental instability, whether they should have access to weapons or not."

Most states mandate that people diagnosed as mentally ill be barred from purchasing a firearm, but critics argue that such laws are not fully enforced.

Reid said he would consider revisiting the mental health provisions from earlier this year, but one "can't separate preventing people with mental illness from buying a gun and background checks."

The White House meanwhile ordered a review into security standards for contractors at federal agencies following Monday's shootings.

The review will be conducted by the White House Office of Management and Budget and will run at the same time as a separate probe into national security clearances launched in the wake of the revelations by fugitive leaker Edward Snowden.