The expiration of the New START Treaty marks a critical moment for international security, UN Secretary-General Antonio Guterres said Wednesday.

He warned that the world now faces no binding limits on the nuclear arsenals of the United States and Russia.

The New START Treaty, which capped the number of strategic nuclear warheads and limited deployment of land- and submarine-based missiles and bombers, expired at midnight Wednesday.

For decades, the treaty acted as a cornerstone of nuclear arms control, helping to regulate the arsenals of the two countries with the largest stockpiles of nuclear weapons.

UN chief raises alarm

“For the first time in more than half a century, we face a world without any binding limits on the strategic nuclear arsenals of the Russian Federation and the United States of America,” Guterres said in a statement.

He warned that the collapse of this framework “could not come at a worse time,” noting that the risk of nuclear weapon use is now at its highest level in decades.

Despite the risks, Guterres said the moment presents an opportunity to establish a new arms control regime.

He called on Russia and the United States to translate their words into action and negotiate a successor framework that restores verifiable limits, reduces nuclear risks, and strengthens global security.

“The world now looks to the Russian Federation and the United States to return to the negotiating table without delay,” he said.