Secretary General Antonio Guterres used an address to the UN's Conference on Disarmament to warn that one of the cornerstones of diplomatic achievement over the last half century -- arms control -- was in "grave danger".

"I will be blunt. Key components of the international arms control architecture are collapsing," Guterres said.

The United States has already begun the process of withdrawing from the Intermediate-Range Nuclear Forces (INF) treaty, in response to Moscow's deployment of the 9M729 missile, prompting Russia to announce its own withdrawal.

"We simply cannot afford to return to the unrestrained nuclear competition of the darkest days of the Cold War," Guterres said.

"I call on the parties to the INF Treaty to use the time remaining to engage in sincere dialogue on the various issues that have been raised," he added. "It is very important that this treaty be preserved."

The collapse of the 1987 treaty, which banned ground-launched missiles with a range of 500 to 5,500 kilometres, has sparked fears of a new arms race in Europe.

The US withdrawal is not set to take effect until August, giving a six-month window to save the treaty, but few expect this to happen and NATO has warned the world should ready itself for the pact's scrapping.