WASHINGTON – An era in arms control ended Friday with the formal unraveling of the 1987 Intermediate-Range Nuclear Forces treaty.

The U.S. suspended compliance with the landmark agreement – which restricted missile launches from both countries – in February, the beginning of a six-month formal withdrawal process, which expired Friday.

Supporters of the move said it was long overdue, because Russia was brazenly violating the treaty and had resisted extensive U.S. pressure to return to compliance. But critics said abandoning the 32-year-old treaty could spark a new arms race, undermine American credibility and put Europe at risk of Russian aggression.

"The president’s decision will increase tensions between the United States and Russia and open the door to a competition in conventionally armed missiles that will undermine stability," said David Wright, co-director of the Global Security Program at the Union of Concerned Scientists.

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Former Soviet leader Mikhail Gorbachev, who negotiated and signed the pact with then-President Ronald Reagan, said the Trump administration's move was a blow to international peace and security.

“This move undermines security not only in Europe, but in the whole world,” Gorbachev told Interfax on Friday.

The Trump administration – along with leaders of NATO – said only the U.S. was abiding by the terms of the agreement, alleging Russia has violated the INF by developing and deploying new missiles that could reach potential targets in Europe.

"Russia is solely responsible for the treaty’s demise," Secretary of State Mike Pompeo said. "The United States will not remain party to a treaty that is deliberately violated by Russia."

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Critics said there is now nothing to prevent Russia from developing new kinds of missiles out in the open – and the United States is likely to respond with new weapons developments of its own.

When he announced in February that the U.S. would withdraw from the INF in six months, Trump said "we will move forward with developing our own military response options and will work with NATO and our other allies and partners to deny Russia any military advantage from its unlawful conduct."

Also blaming Russia for the demise of the treaty, NATO Secretary General Jens Stoltenberg tweeted that his alliance "will respond in a measured & responsible way and continue to ensure credible deterrence & defence."

The late Intermediate-Range Nuclear Forces treaty harkens back to the Cold War era. Reagan and Gorbachev signed the INF in December of 1987. The treaty prohibited Washington and Moscow from fielding ground-launched cruise missiles that could fly between 310 and 3,400 miles.

In light of the demise of the INF, arms control organizations are now worried about the fate of another agreement, the New START treaty.

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It expires in early 2021, noted Thomas Countryman, chairman of the board with the Arms Control Association.

"Without the INF Treaty, as well as the soon expiring New START," he said, "there would be no legally binding, verifiable limits on the world’s two largest nuclear arsenals for the first time in nearly half a century.”

Alexandra Bell, a senior policy director at the Center for Arms Control & Non-Proliferation, said the U.S. should not press for new talks with Russia to prevent a further disintegration of the current arms control framework.

"Russia created the INF crisis by producing, testing, and deploying the 9M729," Bell said in a tweet on Friday. "Now both countries need to work to prevent a bad situation from becoming a terrible one. The first step is to get experts around a table to talk to each other and not at each other about what comes next."