In this Sept. 30, 2013, photo, Rep. Peter King, R-N.Y., walks towards the House Chamber on Capitol Hill, in Washington.

WASHINGTON — An assault weapons ban that Democratic leaders have been reluctant to advance despite strong support among their rank-and-file members in the House just got its first Republican backer — Long Island Rep. Pete King.

“They are weapons of mass slaughter,” King said shortly after his backing became public on Congress’ website Monday.

“I don’t see any need for them in everyday society,” King said.

The Assault Weapons Ban of 2019 was rolled out in February by Rep. David Cicilline (D-R.I.), with 190 other Democrats onboard. An additional 11 lawmakers signed on after mass shootings in El Paso, Texas, and Dayton, Ohio, left dozens of people dead and many more injured, with King being among the most recent.

King had been the lead sponsor of a bill improving background checks when Republicans controlled the House and was already one of a handful of Republicans backing that bill now.

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He had already been considering the assault weapons ban, but the shootings in Ohio and Texas raised the level of urgency.

“I think the assault weapons ban is timely now, especially in view of the shooting in El Paso and Dayton,” King said.

Democratic leaders, however, have chosen to focus on background check legislation that already passed the House. Sources have told the Daily News that the leaders think they can best pressure on Senate Majority Leader Mitch McConnell (R-Ky.) on background checks because public support for them hovers around 90% and better. But they are also concerned that moderate Democrats in swing districts would face a backlash for backing a weapons ban, and are unlikely to pursue one unless they believe it is certain to get 218 votes — the number required to assure passage.

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King stepping forward could encourage other Republicans to do so and prod Democrats in districts that have partisan makeups similar to King’s district, which leans only slightly Republican.

“It might give cover to some other Republicans, it might give some incentive to Democrats,” King said of his move.

Cicilline, a vice chairman of the Congressional Progressive Caucus, hailed King.

“These weapons belong on the battlefield, not in our homes, schools, houses of worship or workplaces,” he said. “I’m pleased that Congressman King has joined this effort. I sincerely hope that more of my Republicans colleagues will put their service to our country and the safety of their constituents ahead of their need to raise campaign money from the gun lobby.”

Some other Republicans who have not signed on but have expressed support for the ban include Florida Rep. Brian Mast, who came out in favor of a ban after the Parkland High School slaughter last year, and Ohio Rep. Mike Turner, who said he supports one after the massacre in his Dayton district.

The step forward on an assault weapons ban came as President Trump seemed to ease away from his pledge after the Ohio and Texas shootings to create “very meaningful background checks.”

Speaking to reporters in New Jersey on Sunday before boarding Air Force One, he only said he was waiting for Congress to report back to him on new ideas. “They’ll come in from Democrats and Republicans. And I’ll look at it very strongly,” Trump said. “But just remember, we already have a lot of background checks. OK?”

The new background check bills would close loopholes that skip checks in private sales and would extend deadlines for federal authorities to conduct checks.

Senate Minority Leader Chuck Schumer slammed Trump for his softening rhetoric.

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“We’ve seen this movie before: President Trump, feeling public pressure in the immediate aftermath of a horrible shooting, talks about doing something meaningful to address gun violence, but inevitably, he backtracks in response to pressure from the NRA and the hard-right,” Schumer said. “These retreats from President Trump are not only disappointing but also heartbreaking, particularly for the families of the victims of gun violence.”

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Schumer continues to insist that proceed with the background check bills from the House.

“The way forward is for Senator McConnell to put the bipartisan House-passed universal background checks bill on the Senate floor for a vote immediately,” he said.

McConnell has tasked some of his Senate committee chairmen with coming up with legislation when Congress returns from the August recess after Labor Day.