President Emmanuel Macron is updating France's nuclear deterrence doctrine as Europe worries about Russia and doubts U.S. protection under Donald Trump. On Monday, Macron will speak at a French submarine base and signal how France thinks about using nuclear weapons. The war in Ukraine and Russia's nuclear threats have shaken Europe's security assumptions. Analysts say some Europeans are looking to France for a backup nuclear guarantee. France is the only nuclear power in the European Union. Macron last laid down policy in 2020 and said France has fewer than 300 warheads. Experts are listening for any stronger promise to protect allies.

The Kremlin says it regrets the expiration of the last remaining nuclear arms pact between Russia and the United States, while President Donald Trump declared he was against keeping its limits and wants a better deal. The end of the New START treaty left no caps on the two largest atomic arsenals for the first time in more than half a century, fueling fears of a new nuclear arms race. Russian President Vladimir Putin expressed readiness Thursday to stick to the pact's limits for another year if Washington agreed. But Trump said he wants a new pact. The treaty was signed in 2010. It was extended in 2021 for five more years.

The last remaining nuclear arms pact between Russia and the United States is set to expire this week, removing any caps on the two largest atomic arsenals for the first time in more than a half-century. The end of the New START Treaty sets the stage for what many fear could be an unconstrained nuclear arms race. Russian President Vladimir Putin has declared his readiness to stick to the treaty's limits for one more year if Washington follows suit, but U.S. President Donald Trump has been noncommittal about extending it. Arms control advocates have warned that the treaty's termination would fuel a renewed arms race.

President Donald Trump has declined to say whether he plans to resume underground nuclear detonation tests. He had seemed to suggest that was a possibility in a social media post this week. The post raised concerns the U.S. would begin testing nuclear weapons for the first time in three decades. The president told reporters, "You'll find out very soon" when he was asked about it. Trump said, "We're going to do some testing" and "Other countries do it. If they're going to do it, we're going to." But he refused to offer more details. He spoke aboard Air Force One as he headed to Florida on Friday for the weekend.

President Donald Trump has appeared to suggest on social media that the U.S. resume testing nuclear weapons for the first time in three decades. There was no indication that the U.S. would start detonating warheads, but the president offered few details about what seemed to be a significant shift in U.S. policy. He made the announcement on social media minutes before meeting with Chinese leader Xi Jinping on Thursday in South Korea. The U.S. military already regularly tests its missiles that are capable of delivering a warhead, but it has not detonated the weapons since 1992 because of a test ban.

Outer space has emerged as the world's next battlefield, demonstrated by recent cyberattacks on satellites blamed on Russia. National security officials have said the Kremlin also is seeking to develop a space-based weapon that could knock out American satellites, potentially devastating the U.S. economy while leaving the country vulnerable to military attack. Officials in Washington are taking notice, investing in greater efforts to defend U.S. satellites while countering threats from China and Russia. One example is the U.S. Space Force, created in 2019 and tasked with protecting American interests in space.