The government called it “the biggest strengthening of the U.K.’s nuclear posture in a generation.”

Starmer made the announcement while attending a NATO summit in the Netherlands. NATO Secretary-General Mark Rutte welcomed the decision, calling it “yet another robust British contribution to NATO.”

The U.K. phased out air-dropped atomic weapons in the 1990s after the end of the Cold War. Its nuclear arsenal now consists of submarine-based missiles.

Only three NATO members – the U.S., Britain and France – are nuclear powers, while seven nations contribute to the alliance’s nuclear mission by contributing jets that can carry either conventional or weapons or American B61 bombs stockpiled in Europe.

The use of nuclear weapons by the U.K. as part of the mission would require the authorization of NATO’s nuclear planning group as well as the U.S. president and British prime minister.

Marion Messmer, from the international security program at the Chatham House think tank, said the government had avoided saying whether U.S. nuclear weapons would be based on British soil, a move that would likely be controversial.

“The U.K. doesn’t have any nuclear weapons itself that could be deployed via this aircraft,” Messmer said. “Other states in NATO that participate in this mission also host U.S. nuclear weapons on their territory – these weapons remain entirely under U.S. control.”

Starmer also announced that the U.K. will provide 350 air defense missiles to Ukraine, funded by 70 million pounds ($95 million) raised from interest on seized Russian assets.

The announcements come as the U.K. and other NATO members pledge to increase spending on security to 5% of gross domestic product by 2035. The total includes 3.5% on defense and another 1.5% on broader security and resilience efforts.

The U.K. currently spends 2.3% of national income on defense and says that will rise to 2.6% by 2027.