European leaders showed a cautiously receptive ear to President Emmanuel Macron's proposal to debate extending the French nuclear umbrella to Europe on Thursday, though some were reluctant to draw a line under years of U.S. protection.

In an address to the nation on Wednesday, Macron said he would launch a strategic dialogue over extending the protection offered by France's nuclear arsenal to its European partners, seizing on comments from future German leader Friedrich Merz.

Although both France and Britain are nuclear powers, most European countries' primary nuclear deterrence comes from the United States, a decades-old symbol of trans-Atlantic solidarity.

But the radical shift engineered by U.S. President Donald Trump's new administration, which has made overtures to Russia, pressured Ukraine to make peace with Moscow, and adopted a more aggressive stance towards traditional allies, has focused minds.

"We Swedes, like most people, want to have as few nuclear weapons as possible, but right now we should be happy and grateful that there are two neighbouring countries that have nuclear weapons," Swedish Prime Minister Ulf Kristersson said.

"So I think it is good that France is showing openness," he told reporters ahead of an EU summit in Brussels, though he said the issue was not on the meeting's agenda on Thursday.

Denmark, once a staunch U.S. ally now shocked by Trump's thinly-veiled threats of taking over Greenland, a Danish territory, also appeared receptive.

"I think we have to discuss everything now, so all good ideas around the table have to be a part of our discussion," said Danish Prime Minister Mette Frederiksen.

Some Baltic countries, which have expressed fears they could be next if Russia was allowed to prevail in Ukraine, showed openness too.

"I think it's a very interesting idea," Lithuanian Prime Minister Gitanas Nauseda said. "A nuclear umbrella would serve as really very serious deterrence toward Russia," he said.