US President Donald Trump says the United States intends to build up its arsenal of nuclear weapons to pressure Russia and China.
The warning came after Russia said it would be forced to respond by increasing its own missile capabilities if Mr Trump carried through on his threat to quit the Intermediate Nuclear Forces Treaty (INF).
The treaty, signed by former US President Ronald Reagan and Soviet leader Mikhail Gorbachev in 1987, required the elimination of short-and-intermediate-range nuclear and conventional missiles by both countries.
Speaking to reporters, Mr Trump repeated his contention that Russia was not abiding by the INF treaty.
"Russia has not adhered to the agreement. This should have been done years ago. Until people come to their senses, we have more money than anybody else by far, we'll build it up until they come to their senses.
"When they do, then we'll all be smart and we'll all stop and by the way not only stop but we will reduce, which I would love to do."
Mr Trump boasted about America's nuclear ability, claiming that "until they get smart, there will be nobody that's going to be even close to us".
He also took aim at "anyone else who want's to play that game" including China, suggesting that they should be included in any new or renegotiated agreement.
Meanwhile in Moscow, Mr Trump's national security advisor John Bolton met with Russian officials, denying Russian allegations the United States was using the threat of treaty withdrawal to blackmail Russia.
Washington had not yet taken any decision on deploying missiles in Europe targeting Moscow in the event that the INF treaty is scrapped, Russia's RIA news agency quoted him as saying.
Mr Bolton said Russia was violating its commitments under the pact, an allegation Moscow has denied.
The European Union warned Mr Trump to assess the potential impact on American citizens and the world of the US withdrawing from a nuclear weapons treaty with Russia and increasing their its arsenal.
The EU statement said the arms control treaty had been an essential cornerstone of Europe's security structure for more than three decades and helped contain the proliferation of weapons of mass destruction.
Kremlin spokesman Dmitry Peskov told reporters earlier on Monday (local time) that the US move to end the treaty would force Russia to increase its own capacity.
"This is a question of strategic security. Such measures can make the world more dangerous," Mr Peskov said of the planned US withdrawal.