Polish and Danish leaders signalled openness today to French President Emmanuel Macron’s proposal to discuss how France’s nuclear deterrent can protect Europe.

“The French proposal is not new. This topic has come up in conversations with me several times,” said Polish Prime Minister Donald Tusk on his way into the summit of European leaders in Brussels Thursday. “This is something worth considering,” he added.

France is the European Union’s only nuclear power, and one of three within NATO — alongside the United States and the United Kingdom.

For years, Macron’s push to discuss the issue with European partners has fallen on deaf ears as European capitals perceived they were protected by Washington’s nuclear deterrent.

But now, U.S. President Donald Trump’s realignment with Russia and threats to pull out American troops from Europe are triggering defense policy shifts in Europe, including in nations historically very close to the U.S. such as Poland and Denmark.