Emmanuel Macron is "still kind of working out" his vision for NATO, a senior US official said Friday, brushing aside the French president's call for reinventing the American-led alliance.

Ahead of next week's NATO leaders' summit outside London, the Trump administration official dismissed the views expressed by Macron, who argues the military bloc is suffering "brain death."

"President Macron is still kind of working out what he wants out of the group," the official told reporters on condition of anonymity.

Macron on Thursday stood by his startling diagnosis of the alliance and called for a shift in priorities away from great powers like Russia or China to confronting the "common enemy" of terrorism.

Macron has courted controversy by pursuing thawed relations with Moscow, despite Russia's ongoing occupation of Crimea in Ukraine and support for separatists in the east of the country.

Russian President Vladimir Putin has also been condemned across Europe for allegedly overseeing assassination campaigns against opponents and exiles.

By contrast, Trump will tell the NATO summit that China and Russia remain major challenges.

"China above all," the US official said.

The official said it was "no wonder" that many other NATO members were worried by Russia's "consistent disregard for the sovereign and territorial integrity of its neighbors."