"This agreement is not directed against Europe or NATO, and there is broad agreement that we should not allow this issue to cause a rift in the Transatlantic alliance," Jens Stoltenberg said after a meeting of national security advisors.

"I understand the disappointment by France, at the same time I'm absolutely confident that allies involved will find a way forward."

The shock announcement last month by the United States, Australia and Britain that they were forming a new pact and that Canberra was ditching a submarine deal with France worth tens of billions of euros enraged Paris.

France withdrew its ambassadors from Washington and Canberra in protest over the move -- although both diplomats have now been sent back to their posts.

The US has scrambled to patch up relations with its oldest ally, with Secretary of State Antony Blinken meeting President Emmanuel Macron in Paris for talks.

Stoltenberg said that allies "do not always see eye to eye on everything, all of the time, but we never lose sight of the big picture".

"At the time of increased global competition, Europe and North America must continue to stand strong together in NATO, the security challenges we face are too great for any country or continent to face alone," he said.