At a summit on Thursday, Prime Minister Keir Starmer and President Emmanuel Macron also announced a “one in, one out” pilot program on migrants crossing the English Channel.

THE HAGUE, Netherlands — France and the United Kingdom, Europe’s two nuclear-armed powers, have agreed to coordinate their atomic arsenals in response to major threats against the continent. The decision comes as part of a series of defense agreements signed by French President Emmanuel Macron and U.K. Prime Minister Keir Starmer on Thursday.

France and Britain on Thursday agreed to reinforce cooperation over their respective nuclear arsenals as the two European powerhouses seek to respond to growing threats to the continent and uncertainty over their U.