The last remaining nuclear arms pact between Russia and the United States is set to expire Thursday, removing any caps on the two largest atomic arsenals for the first time in more than a half-century.

Axar.az, citing AP, reports the termination of the New START Treaty would set the stage for what many fear could be an unconstrained nuclear arms race.

Russian President Vladimir Putin declared readiness to stick to the treaty’s limits for another year if Washington follows suit, but President Donald Trump has been noncommittal about extending it.

Trump has repeatedly indicated he would like to keep limits on nuclear weapons and involve China in arms control talks, a White House official who was not authorized to talk publicly and spoke on condition of anonymity said Monday.

Trump will make a decision on nuclear arms control “on his own timeline,” the official said.