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.

The move appears to offer both countries’ nuclear weapons as a deterrent for all of Europe while establishing greater independence from any safety net provided by the U.S.’s much larger arsenal.