By Steve Holland and Andrew Osborn

WASHINGTON/MOSCOW (Reuters) – The United States formally withdrew from a landmark nuclear missile pact with Russia on Friday after determining that Moscow was in violation of the treaty, something the Kremlin has repeatedly denied.

Washington signaled it would pull out of the arms control treaty six months ago unless Moscow stuck to the accord. Russia called the move a ploy to exit a pact the United States wanted to leave anyway in order to develop new missiles.

The 1987 Intermediate-range Nuclear Forces Treaty (INF) was negotiated by then-U.S. President Ronald Reagan and Soviet leader Mikhail Gorbachev.

FILE PHOTO: U.S. President Ronald Reagan (R) and Soviet President Mikhail Gorbachev sign the Intermediate-Range Nuclear Forces (INF) treaty in the White House December 8 1987. REUTERS//File Photo

It banned land-based missiles with a range of between 310 and 3,400 miles (500-5,500 km), thus reducing both countries’ ability to launch a nuclear strike at short notice.

“The United States will not remain party to a treaty that is deliberately violated by Russia,” Secretary of State Mike Pompeo said in a statement about the U.S. withdrawal.

“Russia’s non-compliance under the treaty jeopardizes U.S. supreme interests as Russia’s development and fielding of a treaty-violating missile system represents a direct threat to the United States and our allies and partners,” Pompeo said.

Senior administration officials, who spoke on condition of anonymity, said Russia had deployed “multiple battalions” of a cruise missile throughout Russia in violation of the pact, including in western Russia, “with the ability to strike critical European targets.”

Russia denies the allegation, saying the missile’s range puts it outside the treaty. It has rejected a U.S. demand to destroy the new missile, the Novator 9M729, known as the SSC-8 by the NATO Western military alliance.

Moscow has told Washington its decision to quit the pact undermines global security and removes a key pillar of international arms control.

RUSSIAN RESPONSE

Russia said on Friday it had asked the United States for a moratorium on the deployment of land-based short and intermediate-range nuclear missiles.

“A serious mistake has been made in Washington,” Russia’s Ministry of Foreign Affairs said in a statement.

“We have already introduced a unilateral moratorium and won’t deploy land-based short or medium-range missiles, if we get them, in regions where such U.S. missiles are not deployed,” it said.

President Vladimir Putin says Russia does not want an arms race and he has promised he will not deploy Russian missiles unless the United States does so first.

However, should Washington take such a step, he says he would be forced to deploy Russian hypersonic nuclear missiles on ships or submarines near U.S. territorial waters.

NATO Secretary-General Jens Stoltenberg dismissed Russia’s moratorium request on Friday, saying it was “not a credible offer” as he said Moscow had already deployed illegal missiles.

“There are no new U.S. missiles, no new NATO missiles in Europe, but there are more and more new Russian missiles,” he said.

The dispute is aggravating the worst U.S.-Russia friction since the Cold War ended in 1991. Some experts believe the treaty’s collapse could undermine other arms control agreements and speed an erosion of the global system designed to block the spread of nuclear arms.

‘WE DON’T WANT A NEW ARMS RACE’

NATO said it had agreed a defensive package of measures to deter Russia. That response would be measured and would only involve conventional weapons, it said.

NATO’s Stoltenberg said there would be “no rash moves” by the alliance which he said “would not mirror what Russia does.”

“We don’t want a new arms race,” Stoltenberg said.

NATO members Britain and Poland blamed Moscow for the INF treaty’s demise.

“Their contempt for the rules-based international system threatens European security,” British Foreign Secretary Dominic Raab said on Twitter.

European officials have voiced concern that if the treaty collapses, Europe could again become an arena for a nuclear-armed, intermediate-range missile buildup by the United States and Russia.

U.S. officials said the United States was months away from the first flight tests of an American intermediate-range missile that would serve as a counter to the Russians. Any deployment would be years away, they said.

“We are just at the stage of looking at how we might further the development of conventional options,” one official said.

The U.S. military plans to test a ground-launched cruise missile in the coming weeks and an intermediate-range ballistic missile in November, both of which would have been banned under the treaty.

But U.S. officials told Reuters that funding would run out for the tests without approval from Congress, where top Democrats have balked at Trump’s treaty pullout.

Trump has said he would like to see a “next-generation” arms control deal with Russia and China to cover all types of nuclear weapons, something Beijing has so far rejected.

(Reporting by Roberta Rampton and Steve Holland in WASHINGTON, Andrew Osborn in MOSCOW and Robin Emmott in BRUSSELS; Additional reporting by Idrees Ali and Phil Stewart; Editing by Jon Boyle, Peter Graff and Edmund Blair)