US-Russia Nuclear Treaty Ends, Sparking Arms Race Fears

The last remaining nuclear treaty between the United States and Russia expired on February 5, ending decades of limitations on the world's two largest nuclear arsenals and raising fears of a new global arms race.

New START, a landmark agreement signed during a period of warmer relations, concluded after President Donald Trump did not follow up on a proposal from Russian President Vladimir Putin to extend the treaty's limits for another year.

An unarmed Minuteman III intercontinental ballistic missile launches from Vandenberg Air Force Base in California during a test on February 5, 2020.

Global Leaders Warn of Unchecked Arsenals

The treaty's expiration prompted immediate international concern. UN Secretary-General Antonio Guterres described the development as a "grave moment for international peace and security" and urged both Washington and Moscow to return to negotiations.

"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 stated. He warned that the risk of a nuclear weapon being used is now the highest in decades, particularly after Russian suggestions of using tactical nuclear weapons in the Ukraine war.

Pope Leo XIV also weighed in, stating that both nations needed to do "everything possible" to prevent a new arms race. "I urge you not to abandon this instrument without seeking to ensure that it is followed up in a concrete and effective manner," the American-born pope said.

Russia Vows Prudence but Prepares Countermeasures

In response, Russia's foreign ministry declared that both countries are "no longer bound by any obligations or symmetrical declarations within the context of the treaty."

While the ministry stated that "the Russian Federation intends to act responsibly and prudently," it also issued a warning. Russia is prepared to take "decisive" countermeasures if its national security is threatened.

Washington's Stance: Why China is the New Focus

The Trump administration has frequently criticized international limits on the United States. The official U.S. position centers on the need to include China in any future arms control agreements.

"The president's been clear in the past that in order to have true arms control in the 21st century, it's impossible to do something that doesn't include China, because of their vast and rapidly growing stockpile," Secretary of State Marco Rubio said on Wednesday.

China’s nuclear arsenal is expanding, with an estimated 550 strategic nuclear launchers. This is still significantly below the 800-launcher cap that New START imposed on both Russia and the United States. U.S. allies France and Britain, also treaty-bound, possess another 100 launchers combined.

A Diplomatic Breakdown?

Some observers suggest the expiration of New START was less about ideology and more a result of a lack of diplomatic bandwidth within the Trump administration, where career diplomats have been sidelined.

The administration’s focus on China was a factor during Trump's first term, with a U.S. negotiator once setting up an empty seat with a Chinese flag at talks. However, when asked in October about Putin’s proposal for a one-year extension, Trump called it "a good idea," though no negotiations followed.

Daryl Kimball, executive director of the Arms Control Association, agreed that China should engage on its nuclear program but questioned the administration's approach. "Despite Trump's talk about involving China in nuclear negotiations, there is no indication that Trump or his team have taken the time to propose risk reduction or arms control talks with China since returning to office in 2025," Kimball noted. He suggested that Trump and Putin could agree to maintain current limits first and then jointly press China to join.

The Rise and Fall of the New START Treaty

The New START treaty was a cornerstone of international security for over a decade. After defeating Trump in the 2020 election, Joe Biden agreed with Russia to extend the treaty for five years, but relations between the two powers later deteriorated following Moscow's invasion of Ukraine.

The original treaty was signed in 2010 in Prague by then-presidents Barack Obama and Dmitry Medvedev. It limited each country's nuclear arsenal to 1,550 deployed strategic warheads, representing a reduction of nearly 30% from the previous limit set in 2002.

U.S. President Barack Obama and Russian President Dmitry Medvedev shake hands after signing the New START nuclear disarmament treaty in Prague on April 8, 2010.