President Trump said Thursday that the United States will withdraw from the Treaty on Open Skies, a nearly 30-year-old pact designed to reduce the chances of an accidental war by allowing mutual reconnaissance flights for members of the 34-country agreement.

Speaking on the White House lawn before flying to Michigan, Trump said the United States was pulling out because Russia has been violating the pact.

“Until they adhere, we will pull out,” he said.

The Trump administration will issue a formal notification Friday that the United States intends to withdraw, the Pentagon said in a statement. That triggers a six-month period, at the end of which the United States will no longer be party to the agreement.

The planned withdrawal marks another example of the erosion of a global arms-control framework that Washington and Moscow began hashing out painstakingly during the Cold War. The Trump administration pulled out of a 1987 pact with Russia governing intermediate-range missiles, citing violations by Moscow, and withdrew from a 2015 nuclear accord with Iran, saying Tehran wasn’t living up to the spirit of it.

The primary remaining pillar of the arms-control framework between the United States and Russia is the New START pact, signed by Presidents Barack Obama and Dmitry Medvedev in 2010. The agreement, which places limits on strategic nuclear platforms such as bombers, submarines and intercontinental ballistic missiles, will expire in February. It can be extended for five years without ratification if the U.S. and Russian presidents both agree.

Russian President Vladimir Putin has said he wants to extend the pact, but the Trump administration has balked, describing it as outdated and lacking in proper oversight.

The Trump administration has been pushing to negotiate a follow-on agreement that includes China in addition to Russia, but China has rejected calls for talks so far. If the pact is not renewed, the world will return to an era without any legally binding or verifiable limits on its two biggest nuclear powers for the first time since 1972.

The withdrawal from the Open Skies treaty risks driving another wedge between the United States and its European allies, some of whom have urged the United States to remain in the pact despite concerns about Russian compliance.

Christopher A. Ford, assistant secretary of state for international security and non-proliferation, said Thursday that Russia had violated the Open Skies agreement by restricting flights over its southern Chechnya region, the exclave of Kaliningrad and along its southern border with Georgia. He said Russia also denied flights over a military exercise that took place in September 2019.

“It’s really regrettable what Russia has done to international arms control,” Marshall Billingslea, the president’s new special representative for arms control, said at an appearance at the Hudson Institute on Thursday. “They really have systematically violated nearly every agreement that they have made — political or legally binding.”

Russia has denied violating the treaty. It criticized the pullout as the Trump administration’s latest reckless dismantlement of major arms control agreements.

“Unfortunately, this is not the first blow to international stability and security being inflicted by the U.S. administration,” Russian Foreign Ministry spokeswoman Maria Zakharova said on the state-run Rossiya-24 television channel.

Advocates of the treaty said that the United States had not exhausted efforts to bring Russia into compliance and that a withdrawal was counterproductive.

“The problems we were having with Open Skies did not defeat the object and the purpose of the treaty,” said Alex Bell, a senior director at the Center for Arms Control and Non-Proliferation. “It never appeared like the Trump administration was really trying to fix these compliance problems. It seems like they only know how to break things.”

Open Skies emerged out of a proposal that President Dwight D. Eisenhower initially suggested to the Soviets to promote transparency about military surveillance overflights.

The Soviet Union rejected his offer, but President George H.W. Bush revived the idea, and the multicountry pact was signed in 1992 after the fall of the Soviet Union. It came into force in 2002, after the 20th nation ratified the agreement.

Today, the treaty includes 34 countries and allows each to carry out reconnaissance flights over one another’s territory on short notice to gather information about military activities.

European allies had been briefed before Thursday’s announcement during meetings with U.S. officials from the Pentagon and the State Department. Some diplomats were told that the United States may still salvage the treaty if Russian behavior changes, but they said the U.S. intention to withdraw seemed clear.

The impending U.S. exit is part of a broader breakdown in arms control that has been occurring for years as Washington locks horns with Moscow. An outcry over Russia’s 2014 invasion of neighboring Ukraine and annexation of Crimea and an uproar over Russia’s 2016 interference in the U.S. presidential election have brought relations between the two powers to a multi-decade low.

In 2002, the George W. Bush administration abrogated the ­Anti-Ballistic Missile Treaty with Russia, paving the way for a U.S. missile defense buildup in Europe. Last year, the Trump administration pulled out of the Intermediate-Range Nuclear Forces Treaty, or the INF Treaty, with Russia, citing Russian violations.

Beyond those pacts, Sen. Tom Cotton (R-Ark.) has pushed for the Trump administration to withdraw from the Comprehensive Nuclear Test Ban Treaty, which has yet to enter into force, as well as the Treaty on Open Skies.

“Like so many treaties with Russia, the Open Skies agreement was negotiated and signed with good intentions, then abused by Moscow for maximum advantage,” Cotton wrote late last year in an op-ed piece in The Washington Post. He has argued that the pact is giving Russia spying capability that Moscow wouldn’t otherwise possess and that it doesn’t give the United States any intelligence that isn’t available elsewhere.

Cotton praised the Trump administration’s decision Thursday, but some Republican elder statesmen criticized the move, including Gen. Michael V. Hayden, a senior intelligence official in the George W. Bush administration. “This is insane,” he tweeted, adding that he previously served as CIA director.

Sen. Robert Menendez (N.J.), the top Democrat on the Senate Foreign Relations Committee, described the administration’s decision to withdraw as reckless. He said Congress mandated that the administration provide a review period before withdrawing from the treaty and accused the administration of risking violating the law by failing to do so.

“The timing of the Trump administration’s decision to withdraw is clearly tied to the political calendar,” Menendez said in a statement. “By rushing this abrupt withdrawal, it is clear the Trump Administration is attempting to bind a future administration from participation in this long-standing and valuable treaty for our nation.”

Russian Foreign Minister Sergei Lavrov said in April that the Trump administration is averse to any limits on its military, particularly over U.S. territory.

“The Americans, the current administration, conceptually, fundamentally have an aversion to any kind of control over American military activity, especially when that control is exercised on or over U.S. territory,” Lavrov said. He said he doubted that other countries would withdraw.

“Will other countries follow the Americans? I doubt it,” he said. “Europeans seem to me to understand that the agreement has added value as an instrument of trust, an instrument of predictability, transparency, and that is how we see it.”

Trump’s envoy said Thursday that the United States would not hesitate to engage in a costly nuclear arms race with Russia and China. He said he had agreed with top Russian arms control officials on a time to begin negotiations on a new pact and urged China to agree to negotiations, as well.

“We know how to win these races, and we know how to spend the adversary into oblivion, and if we have to, we will, but we sure would like to avoid it,” Billingslea said.

Led by former White House national security adviser John Bolton, the Trump administration has moved quickly to rip up legacy arms-control agreements with Russia, arguing that there’s no sense in remaining in treaties if Russia isn’t going to comply and that only by withdrawing can the United States lay the groundwork for new deals calibrated to the modern era.

Members of the arms-control community, however, have argued that these pacts took a long time to negotiate and Washington may not be able to agree on any substantive follow-on pacts with Moscow. They see little progress on new arms control pacts in the Trump administration’s more than three years in office, raising questions about the administration’s ability to replace that which it destroys.

Withdrawal from a treaty that increased transparency and enjoyed unanimous support among U.S. allies “is another sign of how the Trump administration is willing to both increase the risk of conflict and undermine confidence in U.S. security commitments—two key elements that have prevented outright conflict with Russia for a generation,” Derek Johnson, director of the antinuclear weapons advocacy group Global Zero, said in a statement.

Arms control advocates say the administration should exhibit more caution, act in concert with allies and hold on to agreements even if they are flawed while trying to improve them. Ripping them up, they argue, serves only to make the world more dangerous.

“Trashing the legacy of respected Republican presidents like Eisenhower and G.H.W. Bush will put President Trump in the rarefied territory of being the only U.S. leader to have abandoned three arms-control treaties and created none,” Bell said.

Isabelle Khurshudyan in Moscow contributed to this report.