WASHINGTON — The Trump administration is pulling the plug on a decades-old nuclear arms treaty with Russia, lifting what it sees as unreasonable constraints on competing with a resurgent Russia and a more assertive China.

The move announced Friday sets the stage for delicate talks with U.S. allies over potential new American missile deployments.

In explaining his decision, which he had foreshadowed months ago, President Donald Trump accused Moscow of violating the 1987 Intermediate-Range Nuclear Forces treaty with “impunity” by deploying banned missiles. Moscow denies that it is in violation and has accused Washington of resisting its efforts to resolve the dispute.

Democrats in Congress and some arms control advocates criticized Trump’s decision as opening the door to an arms race.

“The U.S. threat to terminate the treaty will not bring Russia back into compliance and could unleash a dangerous and costly new missile competition between the United States and Russia in Europe and beyond,” the private Arms Control Association said.

Trump said in a statement that the U.S. will “move forward” with developing its own military response options to Russia’s banned deployment of cruise missiles that could target Western Europe.

“We cannot be the only country in the world unilaterally bound by this treaty, or any other,” Trump said. Other officials said the treaty could still be saved if Russia reverses course and returns to compliance, but that window of opportunity will close in six months when the American withdrawal is due to take effect.

The Trump decision reflects his administration’s view that the arms treaty was an unacceptable obstacle to more forcefully confronting not only Russia but also China. China’s military has grown mightily since the treaty was signed, and the pact has prevented the U.S. from deploying weapons to counter some of those being developed in Beijing.

Leaving the INF pact, however, risks aggravating relations with European allies, who share the administration’s view that Russia is violating the treaty but who have not endorsed a U.S. withdrawal.

Secretary of State Mike Pompeo, speaking to reporters after Trump’s statement, said Russia will be formally notified today that the U.S. is withdrawing from the treaty, effective in six months. In the meantime, starting today, the U.S. will suspend its obligations under the treaty.

Pompeo said that if, in the coming six months, Russia accepts U.S. demands that it verifiably destroy the cruise missiles that Washington claims are a violation, then the treaty can be saved. If it does not, “the treaty terminates,” he said.

Administration officials have dismissed concerns that the treaty’s demise could trigger a race to develop and deploy more intermediate-range missiles. U.S. officials have emphasized their fear that China, which is not party to the treaty, is gaining a significant military advantage in Asia by deploying large numbers of missiles with ranges beyond the treaty’s limit. Whether the U.S. will now respond by deploying INF noncompliant missiles in Asia is unclear.

In any case, it seems unlikely that Beijing would agree to any negotiated limits on its weaponry.

Russia accused the U.S. of unilaterally seeking to neuter the treaty.

“I ‘congratulate’ the whole world; the United States has taken another step toward its destruction today,” said Konstantin Kosachev, head of the foreign affairs committee in Russia’s upper house of parliament.

The INF treaty was the first arms control measure to ban an entire class of weapons: ground-launched cruise missiles with a range of 310 miles to 3,400 miles. At the time, in the late stages of the Cold War, the U.S. and its allies were mainly concerned by the perceived threat of Russian medium-range nuclear missiles that were targeted at Europe.

U.S. pulls The U.S. deployed similar missiles in response, in the 1980s, leading to negotiations that produced the INF Treaty.

Rep. Adam Smith, a Washington state Democrat and new chairman of the House Armed Services Committee, blasted Trump for raising the risk of nuclear war.

“The administration’s ideological aversion to arms control as a tool for advancing national security is endangering our safety, as well as that of our allies and partners,” Smith said.

U.S. officials say they have little reason to think Moscow will change its stance in the next six months.

“We have raised Russia’s noncompliance with Russian officials — including at the highest levels of government — more than 30 times,” Pompeo said.

Jens Stoltenberg, the NATO secretary-general, said in an interview Friday that Russia can still save the treaty by returning to compliance before the U.S. withdrawal takes effect.

“But at the same time, we have started to assess the consequences, look into options,” Stoltenberg said. “We need to make sure that we respond as an alliance, all 29 allies, because all allies are involved and all allies are affected.”