Washington (AFP) - Democrats unveiled landmark gun safety legislation Tuesday five days after regaining the US House majority, seeking swift action on a measure to expand background checks on firearm sales.

A similar bill was introduced last year by Democrats, but Republican leaders declined to bring it to a vote.

The new bill -- which has the backing of former congresswoman Gabrielle Giffords, who survived being shot in the head eight years ago to the day and is now one of the nation's leading gun control advocates -- has a handful of Republican co-sponsors, and is likely to pass the chamber.

But it is not expected to advance in the Senate, which is under Republican control.

Giffords joined House Speaker Nancy Pelosi and congressman Mike Thompson, who heads a Democratic task force on gun violence, in introducing the bill, calling for "courage" among lawmakers.

"Now is the time to come together, be responsible. Democrats, Republicans, everyone," she said. "We must never stop fighting."

Pelosi said that by introducing the legislation early in the new congressional session, Democrats are saying "enough is enough, by finally bringing commonsense bipartisan background check legislation to the floor."

Thompson said nearly 250,000 Americans have died from gun violence, including suicides, since the Giffords shooting in 2011, "all the time while Congress stood by and did nothing."

"But today is a new day," he said, adding that the vast majority of Americans support the measures.

The bill would expand background checks to all gun sales, closing loopholes in federal law requiring criminal background checks when firearms are sold by licensed dealers but allowing private citizens to sell and transfer guns to one another without any background check.

Democrats have savaged congressional Republicans for repeatedly failing to take action to prevent gun violence after tragedies like the Sandy Hook elementary school shooting in Connecticut in 2012, or the massacre at a Las Vegas concert in October 2017.

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After a murderous rampage at a Florida high school last February left 17 students and staff dead, some Democratic congressional candidates campaigned on pledges to enact gun safety reform.

One of them, Georgia's Lucy McBath, whose son was murdered in 2012, won a congressional seat in November's election.

"By closing these loopholes and expanding background checks, we will make our communities safer," she said.

"States that have already expanded background checks have lowered their homicide rates, their murder rates and their gun trafficking."

Last month, President Donald Trump's administration moved to ban bump stocks, devices that allow semi-automatic weapons to fire like machine guns and that were used in the Las Vegas shooting.