The Trump administration announced its intent to pull out of an important nuclear arms treaty with Russia, due to alleged violations of the treaty by Vladimir Putin’s government.

The decision has stoked fears among diplomats that a new arms race with Moscow could begin.

President Donald Trump, in a statement announcing the US’ withdrawal from the treaty known as the Intermediate-Range Nuclear Forces (INF) Treaty, claimed Russia had been violating the Treaty for years, a claim which Russia has denied.

The Russian violations of the treaty would put the US at a military disadvantage: “We cannot be the only country in the world unilaterally bound by this treaty, or by any other,” Trump said. While the US has obeyed the treaty, other countries uninvolved in the treaty, such as China and Iran, have continued to build their supplies of missiles.

The Treaty, created in 1987, bans the deployment of ground-based missiles that have a range of 500 to 5,500 kilometers, or 310 to 3,410 miles. The destruction of any of these missiles is also required by the treaty.

The Trump administration contended in a statement that Russia “has produced and fielded multiple battalions of its INF-violating, nuclear-capable missile, which threaten our allies and troops in Europe and Asia.” However, Russia replied with an accusation that the US has violated the treaty by creating missile defense systems throughout Europe. The US State Department, in turn, has denied this allegation.

Although the US withdrawal has been made official now, the treaty will officially expire in August. The Trump administration said in a statement that the treaty can only be saved by Russia’s “complete and verifiable destruction of its INF-violating missiles, their launchers, and associated equipment.”

In a statement, the Trump administration mentioned plans to move forward with creating its own intermediate-range missile system. This has furthered fears among policy experts that a second, Cold War-style arms race between the US and Russia will commence. Frederica Mogherini, EU foreign policy chief, said she was concerned about Europe “going back to being a battlefield.”

However, “#NATO fully supports the US suspension & notification of withdrawal from the Treaty,” NATO Secretary General Jens Stoltenberg said on Twitter.

Many Republicans in Congress have applauded the Trump administration’s decision to pull out, saying Russia’s violations of the treaty can not be ignored: “The time has come to set the treaty aside and develop alternative avenues toward the security the treaty once provided,” said Senate Foreign Relations Committee Chairman Jim Risch, a Republican from Idaho. On the other hand, Democrats are worried that with no treaty to restrict the development of intermediate-range missiles, Russia will accumulate more of these missiles.

“The Trump Administration is risking an arms race and undermining international security and stability,” House Speaker Nancy Pelosi, a Democrat from California, said in a statement.

“Honestly, I don’t think she has a clue … I don’t think Nancy has a clue,” Trump responded at the White House.

Although some are worried, the US has maintained hope that a new treaty will be created to re-establish security: “The United States remains committed to effective arms control that advances United States, allied, and partner security, but arms control agreements must be verifiable and enforceable and include partners that comply responsibly with their obligations,” the Trump administration said in a briefing.