"Yes we need a second life insurance, not in substitution to or against NATO but in addition" to the alliance, Stephane Sejourne said alongside his German and Polish counterparts.

He was referring to a speech Trump gave Saturday when he said he would "encourage" Russia to attack members of NATO who had not met their financial obligations.

Sejourne insisted that it was necessary to build on the European element of NATO and build up its own defence industry and "buy European within the framework of our defence industries and prepare in the event of conflict".

Trump's comments at a campaign rally prompted stark warnings at home and abroad that he was putting the military alliance in peril, renewing doubts over the US commitment to the mutual defence treaty if the former president and current Republican frontrunner wins in November.

"The Atlantic alliance is not a contract with a security company," said Polish Foreign Minister Radoslaw Sikorski.

Recalling that Poland sent troops as part of NATO forces in Afghanistan after the September 11, 2001 attacks on the US, he said that then "we did not send the bill to Washington".

French President Emmanuel Macron has himself repeatedly talked up the importance of Europe building its own strategic autonomy and being less dependent on the United States, especially after Russia's invasion of Ukraine.

"We need to take care of the security of Ukrainians, and that means taking care of our security, and yes I think we need a union of defence and security, with joint purchases and pooling our forces," said German Foreign Minister Annalena Baerbock.