WASHINGTON — The National Rifle Association Thursday backed restrictions on bump stocks like the ones used by the Las Vegas shooter to create more deadly weapons.

The powerful gun lobby’s green light is the strongest sign yet that Republicans – long resistant to gun control measures – would back a limited ban on the after-market accessories.

“The NRA believes that devices designed to allow semi-automatic rifles to function like fully-automatic rifles should be subject to additional regulations,” said Wayne LaPierre, the NRA’s CEO, and Chris Cox, executive director of the NRA Institute for Legislative Action, in a joint statement.

The bump stock debate ignited this week after it was revealed that gunman Stephen Paddock used the accessory to make his semi-automatic weapons act like automatics and inflict maximum damage as he sprayed bullets into a country music festival from his 32nd-story hotel room.

He killed 58 people and injured nearly 500 others in the deadliest mass shooting in modern American history.

The White House signaled an openness to banning bump stocks as the NRA announced its support.

“We’re certainly open to that moving forward, but we want to be part of that conversation as it takes place in the coming days and weeks,” said Press Secretary Sarah Huckabee Sanders.

Republicans in Congress, traditionally opposed to any new gun restrictions, showed interest in taking on bump stocks.

“I didn’t even know what they were until this week, and I’m an avid sportsman,” House Speaker Paul Ryan said in an interview Thursday with Hugh Hewitt.

“I think we’re quickly coming up to speed with what this is. Fully automatic weapons have been banned for a long time. Apparently, this allows you to take a semi-automatic, turn it into a fully automatic, so clearly that’s something that we need to look into.”

Meanwhile, Rep. Adam Kinzinger (R-Ill.) is leading a bipartisan effort to have the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) review its 2010 and 2012 decisions that bump stocks were compliant with federal law.

This is the regulatory approach the NRA supports.

A new decision by the AFT could effectively ban the devices without congressional action.

Bump stocks are a “way to circumvent a law (against fully automatic weapons) that was put into effect for very good reasons,” Kinzinger said in an interview Thursday.

“I think the ATF can do this quickly. They can make a determination. If they drag their heels on it … we’ll look at legislative solutions,” he said.

Like many members of congress, Rep. Peter King (R-L.I.) wasn’t familiar with bump stocks until the deadly shooting. He’s said he’d support eliminating them. “I don’t see any rationale” for them, King told The Post.

But Congress shouldn’t stop there, he said. Next week, he’ll reintroduce his bipartisan expanded background check bill, as he does every year.

King’s co-sponsor, Rep. Mike Thompson (D-Cal.), also said he’d vote to ban bump stocks, but he warned that’s not nearly enough to curb gun violence.

“I’m not going to stop fighting for background checks,” Thompson said in an interview Thursday.

“…If this majority believes that a bump stock prohibition is enough, they’ve been smoking something. It just doesn’t even come close.”

Rep. Gregory Meeks (D-Queens) remained skeptical the GOP Congress will sign onto any kind of gun control.

“I’m discouraged at this point because I’ve seen it too often before,” Meeks told The Post.

At the very least, Congress should try to close loopholes in existing gun laws, he said.

“At this point,” Meeks said, “I’ll take any kind of win.”