"The announcement by Russia that it's suspending participation in New Start is deeply unfortunate and irresponsible," said Secretary Blinken.
"We'll be watching carefully to see what Russia actually does. We'll of course make sure that in any event we are postured appropriately for the security of our own country and that of our allies," he added.
The 2010 treaty is the last major US-Russia arms control pact still in force but it has frayed in recent years, with accusations from Washington that Moscow was not complying with it.
"We remain ready to talk about strategic arms limitations at any time with Russia, irrespective of anything else going on in the world or in our relationship," Blinken told reporters at the American embassy in Athens during a regional visit.
He was speaking after Russian President Vladimir Putin announced Moscow's suspension of its participation in the last remaining arms control treaty between the world's two main nuclear powers.
"I am forced to announce today that Russia is suspending its participation in the Strategic Arms Reduction Treaty," said Putin.