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.

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.

While nuclear coordination is set to deepen under the agreement, as is nuclear research cooperation between France and Britain, the document makes it clear that the atomic arsenals will not be fused entirely.