Transcript for Vladimir Putin promised that Russia is developing new intermediate range weapons

And word tonight that Russia is pulling a plug on the nuclear arms pact with the U.S. Suspending the treaty dating back to the Reagan era. Observers say it all may signal a new arms race. Here's ABC's Lana Zak. Reporter: Tonight, experts are warning of a new cold war as one of the most crucial arms-race treaties in history collapses. Russian president Vladimir Putin has promised that Russia is developing new intermediate-range weapons in response to the U.S. Putin is getting his cake and eating it too, because he's able to deploy missiles that now threaten nato, but claim that it's the U.S. That has withdrawn Reporter: They could test an array of weapons, out of a bond-villain playbook. Including this, the poseidon underwater nuclear-powered drone, a device that if successful, would literally create tsunamis. One side has not been adhering to it. We have, but one side hasn't. Unless they're going to adhere we shouldn't be the only one. Reporter: Putin said he's only following America's lead. But for years, Russia has been threatening to withdraw from the landmark 1987 treaty signed by president Ronald Reagan and soviet leader Mikhail gorbachev. In a statement, the president's actions are allowing for a dangerous arms race in which Russia can act with impunity. Tom. Lana, thank you. And be sure to join us on Tuesday night for complete live coverage of the state of the union address and the democratic response.

This transcript has been automatically generated and may not be 100% accurate.