(AP) — Xi’s engagement with Trump and Putin comes as the last remaining nuclear arms pact, known as the New START treaty, 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.

Trump, a Republican, has indicated he would like to keep limits on nuclear weapons but wants to involve China in a potential new treaty.

“I actually feel strongly that if we’re going to do it, I think China should be a member of the extension,” Trump told the New York Times last month. “China should be a part of the agreement.”