By announcing its intent to withdraw from a decades-old nuclear weapons treaty, the United States is targeting Russia, which it says violated the bilateral deal -- but also China, which is developing arms that are banned under it.
Beijing is not a signatory to the Intermediate-Range Nuclear Forces Treaty (INF), so it's Russia that has been singled out for violating the accord, signed in 1987 by Ronald Reagan and Mikhail Gorbachev.
At issue is Moscow's new 9M729 ground-based missile system, which Washington says has a reach that exceeds 500 kilometers (300 miles) -- a claim the Kremlin denies.
"Russia has not unfortunately honored the agreement, so we're going to terminate the agreement and we're going to pull out," U.S. President Donald Trump said Saturday at a campaign rally in Nevada.
Trump did not say whether a new treaty could be negotiated, but he has repeatedly in recent days pointed the finger of blame at both Moscow and Beijing, saying the U.S. would develop its own weapons until they stop.
"Until people come to their senses, we will build it up," Trump told reporters Monday at the White House, referring to the U.S. arsenal.
"It's a threat to whoever you want. And it includes China and it includes Russia and it includes anybody else that wants to play that game."
For several years, Washington has accused Russia of violating the INF Treaty, which banned an entire class of nuclear and conventional missiles with ranges of 500 to 5,500 kilometers (310-3,400 miles).
The accord helped end a crisis begun in the 1980s with the deployment of Soviet SS-20 nuclear warheads targeting Western capitals.
U.S. National Security Advisor John Bolton was dispatched to Moscow for emergency talks, where he said there would be wider consultations with "other" participants.
He told Moscow's Echo radio that "friends" in Europe and Asia could be involved.
For John Lee, a senior fellow at the conservative Hudson Institute think tank who specializes in defense strategy, "the situation vis-a-vis China, uninhibited by any agreement, is very different and far more pressing" than that of Russia.
Mattis 'completely' in line with Trump
In recent years, China has developed "land-based intermediate missiles (capable of carrying conventional and nuclear payloads)," Lee said in a column published Monday on CNN's website.
About 95 percent of the missiles available to the Chinese People's Liberation Army Rocket Force would violate the INF Treaty if Beijing were a signatory, Lee charges.
On the issue, the White House and the Pentagon are on the same wavelength.
Defense Secretary Jim Mattis "is completely aligned with the president and he's in close contact with the president on this," said Pentagon spokesman Colonel Rob Manning.
In its latest Nuclear Posture Review published in February 2018, the Pentagon said: "In the nuclear context, the most significant Russian violation involves a system banned" by the INF Treaty.
But the document also refers to missiles developed by China, which has in recent years sought to assert its military supremacy in Asia.
At the start of October, Mattis put Russia on notice that its continued alleged violation of the arms treaty would not be ignored.
"Russia must return to compliance with the INF Treaty or the U.S. will need to respond to its cavalier disregard for the treaty's specific limits," Mattis said after a meeting of NATO defense ministers in Brussels.
"Make no mistake -- the current situation with Russia in blatant violation of this treaty is untenable."
In a sign that the Pentagon was preparing for an INF withdrawal for months, the new Missile Defense Review -- U.S. policy on ballistic missiles -- has not yet been published, despite its expected arrival in early 2018.
For months, the Defense Department has repeatedly said the policy document will be available "in a few weeks."
When asked about the MDR, Manning said he had no precise publication date to announced, but he highlighted that "all factors will be taken into account before the Missile Defense Review is released."