The United States on Friday renewed pressure on China to join nuclear arms control talks with Washington and Moscow, seeking to overcome Beijing's long-standing opposition to entering such a dialogue.
"China has long said it will never enter into an arms race and does not seek numeric parity with the US and Russia. Now is the time for China to put its money where its mouth is, and prove that it is a responsible international actor," said a senior Trump administration official.
The official was one of several who briefed reporters on condition of anonymity.
The nuclear arsenals of the United States and Russia dwarf that of China. But Beijing's military buildup in the Asia-Pacific region has alarmed US allies and policymakers.
President Donald Trump has sought to entice China into joining the United States and Russia in talks on an arms control accord to replace the 2010 New START treaty between Washington and Moscow that expires next February.
China has rejected Trump's proposal, arguing that its smaller nuclear force is defensive and poses no threat.
"Continued silence from China creates uncertainty about their intentions and only brings about the need for a renewed focus on deterrence and military readiness for the United States," said one administration official.
New START maintains the only remaining limits on US and Russian nuclear deployments. Some experts and lawmakers have called Trump's proposal to include Beijing in a new treaty a "poison pill" strategy aimed at killing New START and ending the restraints on US deployments.
New START restricted the United States and Russia to deploying no more than 1,550 nuclear warheads, the lowest level in decades, and limited the land- and submarine-based missiles and bombers that deliver them.
It can be renewed for up to five years if both sides agree. Moscow has offered to immediately extend the treaty. Washington has yet to decide.
"On New START, we have made no decision on a possible extension as we are focused on addressing a broader range of threats beyond just the weapons subject to the treaty," said an official.
China is estimated to have about 300 nuclear weapons.
The official said China, "as a major military power," also has major responsibilities.
"You cannot ask for global status without assuming global responsibilities for world order and this is why we believe it is high time for China to participate in arms control alongside the United States," the official said.