WASHINGTON (AP) — The White House has not made a decision about whether to extend the only treaty that constrains U.S. and Russian nuclear forces because administration officials want more time to coax China into a three-way arms control pact.

China, which is poised to at least double the size of its nuclear stockpile in the next decade, has not publicly expressed any interest in such talks. A senior administration official, who briefed reporters at the White House on Friday, said Beijing’s continued silence only raises questions about its intentions and will force America to strengthen its deterrence and military readiness.

The administration official, who spoke only on condition of anonymity according to White House ground rules, said the U.S. and Russia support the idea of engaging China to avert a costly nuclear arms race. American allies, however, also are concerned that the Trump administration will not take Moscow up on its offer to extend the New START treaty for up to five years. The treaty, which governs the number of U.S. and Russian strategic nuclear weapons, expires in February 2021.

“So far — and this is not surprising — the Chinese are not interested in arms control,” national security adviser Robert O’Brien said earlier this week at the Atlantic Council. “They’ve got the money, and they’re moving ahead very quickly on every type of advanced platform and weapons system known to man, whether it’s space-based, cyber-based, all different types of kinetic systems.”

“I think we’re hopeful that if we can move forward with the Russians … that there will be pressure on the Chinese, or there will be a desire on the Chinese part not to … incur the expense of an arms race.”

It’s unclear how much time the Trump administration is willing to wait on the Chinese to engage in an arms control discussion. As the treaty’s expiration date nears, the U.S. might agree to extend New START to provide more time to get China into a three-way agreement, the administration official said.