With Washington increasingly focused on the strategic challenge from China, Florence Parly said, "a question mark has emerged" over the transatlantic alliance.

Those posing the question would not be reassured, she said, "by the current atmosphere of withdrawal: withdrawal from battlefields, from treaties, from trade pacts."

"What Europeans are worried about is this: will the US commitment (to NATO) be perennial? Should we assume that it will go on as was the case in the past 70 years?" Parly asked the Atlantic Council in Washington ahead of a meeting with Acting Defense Secretary Patrick Shanahan.

The minister said she was most concerned about President Donald Trump apparently tying the US commitment and Europe's readiness to spend more on defense, including buying more US defense equipment.

"The alliance should be unconditional, otherwise it is not an alliance. NATO's solidarity clause is called Article V, not article F-35," she said, referring to the US fighter jet.

Parly conceded Trump's criticism that NATO's European members need to spend more on shared defense, but she said it would be good to build up a measure of autonomy so as not to overly depend on the US military.

The Europeans "have started to look honestly at what they would be really able to do if left on their own," she said.

"Building a European autonomy should never be seen as a move against the US. We want America solidly steeped in NATO. Autonomy should be a variation on friendship."

"Every time the US has retreated from Europe, threats have come back to haunt the US itself," she added.

Parly also gave support for the continued presence of US forces in Syria, and said France could take part -- an issue she would be discussing with Shanahan.

"Today, we are carefully studying the recent US offer to maintain a residual presence, in cooperation with a few partners," she said.