MOSCOW — President Vladimir V. Putin of Russia, in a decision that was widely expected, suspended his country’s observance of a key nuclear arms control pact on Saturday in response to a similar move by the United States a day before.

But adding to a sense that the broader architecture of nuclear disarmament has started to unravel, Mr. Putin also said that Russia would build weapons previously banned under the treaty and would no longer initiate talks with the United States on any matters related to nuclear arms control.

The Trump administration withdrew from the treaty, a keystone of the late Cold War disarmament pacts known as the Intermediate-Range Nuclear Forces Treaty, saying that Russia had been violating it for years. The decision holds the potential to initiate a new arms race, not only with Russia, but also China, which was never a signatory to the 1987 treaty.

Beijing responded to the American announcement by warning on Saturday that the breakup of the treaty would undermine global security, but also by rejecting calls for China to join an expanded version of the pact.