The United States has formally withdrawn from a landmark nuclear missile pact with Russia after determining that Moscow is in violation of the treaty, something the Kremlin has repeatedly denied.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 US wanted to leave anyway 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 land-based missiles with a range of between 310 and 3400 miles (500-5500km), thus reducing both countries’ ability to launch a nuclear strike at short notice.

The landmark arms control treaty that President Ronald Reagan signed with Soviet leader Mikhail Gorbachev three decades ago is dead. Photo: AAP

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

“Russia’s non-compliance under the treaty jeopardises 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,” Mr 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 US demand to destroy the new missile, the Novator 9M729, known as the SSC-8 by the NATO Western military alliance.

Russian tactical ballistic missile OTR-21 Tochka-U (L), 122mm multiple rocket launcher BM-21 Grad (2-L), tactical ballistic missile 9K720 Iskander-M (C) and 300mm multiple rocket launcher BM-30 Smerch (R) at a military exhibition in Luga, outside St. Petersburg, Russia. Photo: AAP

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

Russia said on Friday it had asked the US 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 US 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 US 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.

All @NATO Allies agree that Russia’s development & deployment of the SSC-8 nuclear-capable cruise missile is a clear violation of the #INFTreaty. 🇷🇺 first denied the missile existed, then when confronted with proof, lied about the missile's capability. #Russia is not being honest pic.twitter.com/HtTmdZHSMp

— U.S. Mission to NATO (@USNATO) August 1, 2019

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

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 Mr 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,” Mr 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.

-with AAP