WASHINGTON/MOSCOW — 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, but Russia said that was a ploy to exit a treaty it said 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-US President Ronald Reagan and Soviet leader Mikhail Gorbachev.

It banned both sides from stationing in Europe land-based missiles with a range of between 310 and 3,400 miles (500-5,500 km), reducing their 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 US withdrawal.

"Russia's non-compliance under the treaty jeopardizes US 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 Russian 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 also rejected a U.S. demand to destroy the new missile, the Novator 9M729, which is known as the SSC-8 by the North Atlantic Treaty Organization.

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

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

"We have proposed to the United States and other NATO countries that they weigh the possibility of declaring the same kind of moratorium on the deployment of short and intermediate range missiles as ours," Deputy Foreign Minister Sergei Ryabkov was quoted as saying by the TASS news agency.

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 US territorial waters.

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

"There are no new US missiles, no new NATO missiles in Europe, but there are more and more new Russian missiles," he said.

The dispute is aggravating the worst US-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.

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

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.

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

The 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.

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. — Reuters