Donald Trump has announced that the US will withdraw its support for a United Nations treaty regulating the multibillion-dollar global arms trade.

Addressing the National Rifle Association (NRA) in Indianapolis, the president said he would revoke America’s status as a signatory of the arms trade treaty regulating conventional weapons including small arms, battle tanks, combat aircraft and warships.

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“My administration will never ratify the UN arms trade treaty,” Trump said. “We’re taking our signature back. The United Nations will soon receive a formal notice that America is rejecting this treaty.”

Trump added: “Under my administration, we will never surrender American sovereignty to anyone. We will never allow foreign bureaucrats to trample on your second amendment freedom. I’m officially announcing today that the United States will be revoking the effect of America’s signature from this badly misguided treaty.”

The US signed the treaty in 2013 but never ratified it. The NRA has long claimed the treaty poses a threat to the second amendment. On Friday its members stood, applauded and chanted “USA! USA!” as Trump signed a letter to Congress halting the ratification process, then tossed his pen into the crowd.

A delighted Chris Cox, executive director of the NRA’s Institute for Legislative Action, said: “Barack Obama and John Kerry tried to force us to accept international gun control under the power of the UN, but Donald Trump has said: ‘Not on my watch.’”

But the move drew sharp criticism.

Bob Menendez, top Democrat on the Senate foreign relations committee, said: “This is yet another myopic decision that jeopardizes US security based on false premises and fearmongering. While Americans from all walks of life have come to painfully understand the threat posed by not doing enough to prevent weapons from ending up in the wrong hands, it is disturbing to see this administration turn back the clock on the little progress we have made to prevent illicit arms transfers.”

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The Senate has so far failed to approve the treaty because of Republicans’ “paralyzing fear of backlash from the NRA”, Menendez added. “This is another reminder that if we’re going to get anywhere to break the inaction on the kind of commonsense steps to stop gun violence and keep people safe, we must stop letting the NRA set the agenda in Washington.”

Rachel Stohl, the managing director of the Stimson Center thinktank in Washington, and a consultant to the arms trade treaty process, said: “Today the president once again walked away from America’s leadership role in the world and undermined international efforts to reduce human suffering caused by irresponsible and illegal arms transfers.

“Un-signing the treaty will undermine international peace and security, increase irresponsible and illegal sales of conventional weapons, and harm the American economy.”

Beset by internal turmoil, financial troubles and a public backlash following mass shootings, the NRA, which has 5.5 million members, welcomed the chance to rally around Trump, the first president to address its annual convention for three consecutive years. Thousands gathered at the Lucas Oil Stadium, many wearing red Make American Great Again caps.

Pledging to defend the second amendment, Trump warned: “In recent days Democrats have proposed banning new guns and confiscating existing guns from law abiding citizens. What they don’t tell you is the bad guys don’t give up their guns. And you’re not going to be giving up your guns either.”

He also raged against special counsel Robert Mueller’s investigation into Russian election interference. “They tried for a coup; didn’t work out so well. And I didn’t need a gun for that one, did I?”

Trump added that he has seen “corruption at the highest levels. A disgrace. Spying. Surveillance. Trying for an overthrow, and we caught ‘em. We caught ‘em … Democrats are obsessed with hoaxes, delusions and witch-hunts. We can play the game just as well or better than they do.”

Facebook Twitter Pinterest The audience listens to Trump’s speech. Photograph: Tannen Maury/EPA

In lines reminiscent of a Trump campaign rally, the president also touted the economy, promised to build 400 miles of border wall by the end of next year and complained: “The level of corruption and dishonesty in the media is unbelievable.”

Earlier, the vice-president, Mike Pence, returning to his home state, predicted: “Despite the fact that this president has faced unprecedented opposition, obstruction, and resistance, I believe that when this president’s story is written, when he finishes his term in office, six years from now, I believe history will record: no other president in all the modern era has done so much for so many in so little time. President Trump has delivered.”

Pence warned of the threat of socialism and took a swipe at Democratic candidate Bernie Sanders over his proposal to allow prison inmates to vote. “The same people who want to restrict the right to keep and bear arms of law-abiding citizens believe the Boston Marathon bomber should be given the right to vote on death row. I got news for you, Bernie: not on our watch!

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“Violent convicted felons, murderers, and terrorists should never be given the right to vote in prison – not now, not ever.”

The partisan political messages appeared to resonate with NRA members. Shelley Grafmyre, 68, a registered nurse from Elgin, Illinois, did not vote for Trump or Hillary Clinton in 2016 but will back the president next year. She said of Democrats: “They’re liars; they can’t con me. Every one of them is going so far left. Confiscating guns is their goal. I’m a senior woman who likes to protect herself and go shooting. Leave me the hell alone.”

Charlie Morgan, 67, a retired police officer from Chicago, said: “I’m disgusted with Democrats. Ever since the Brett Kavanaugh hearings and the way they treated that man with his kids in the room, I would never vote for another Democrat. They’ve lost me ever since that hearing.”

Reinhold Toerek, 62, an engineer from Cleveland, Ohio, joined the NRA a month ago. “What prompted me to do it was the threat of our second amendment rights being lost. I think the antagonism between the Republicans and the Democrats because of Trump has heightened the threat to the second amendment and we have to do our bit to protect it.”