Pope Leo issues urgent appeal to save last major US-Russia nuclear arms pact

Pope Leo, on February 4, called on leaders in Russia and the United States to renew the New START nuclear arms control treaty, warning that the current global climate makes it essential to prevent a new arms race.

Speaking during his weekly audience at the Vatican, the first US-born pope said the world situation “calls for doing everything possible to avert a new arms race,” and issued an urgent appeal for the agreement not to be allowed to expire.

“I issue an urgent appeal not to let this instrument lapse,” Leo said. “It is more urgent than ever to replace the logic of fear and distrust with a shared ethic, capable of guiding choices toward the common good.”

The New START treaty, which limits the number of active missiles and nuclear warheads held by the world’s two largest nuclear powers, is set to expire on February 5. Its expiration would mark the end of more than half a century of formal constraints on nuclear arsenals between Washington and Moscow.

Signed on April 8, 2010, in Prague by then US President Barack Obama and Russian President Dmitry Medvedev, the Strategic Arms Reduction Treaty entered into force in 2011 as part of long-running efforts to curb strategic nuclear forces. The agreement established binding caps on deployed strategic warheads and delivery systems, while introducing verification measures such as on-site inspections and regular data exchanges aimed at increasing transparency and predictability.

Under the treaty, each side is limited to 1,550 deployed strategic nuclear warheads and 700 deployed delivery vehicles — including intercontinental ballistic missiles, submarine-launched ballistic missiles, and heavy bombers — within an overall ceiling of 800 deployed and non-deployed launchers. Unlike earlier agreements, New START counts actual warheads, providing a more precise picture of each country’s nuclear arsenal.

The pact was extended for five years in 2021, but its verification regime has been weakened in recent years as mutual inspections were suspended amid rising geopolitical tensions, including over Russia’s invasion of Ukraine.

In September, Russian President Vladimir Putin proposed that the treaty could be informally extended for another year. However, as of Wednesday, US President Donald Trump had not responded to the proposal.

Pope Leo warned that allowing the treaty to lapse would remove one of the last remaining pillars of global nuclear arms control at a time of growing instability, urging both sides to act in the interest of international security.

By Tamilla Hasanova