BRUSSELS, June 3 - The U.S. expects European NATO allies and Canada to swiftly increase the number of manned and unmanned aircraft and ships they contribute to the alliance's defence plans as Washington steps back in these areas, a top U.S. general said on Wednesday.

The statement by U.S. Air Force General Alexus Grynkewich, NATO's top commander and the head of U.S. forces in Europe, followed a decision by the Trump administration to shrink the pool of U.S. military capabilities available to NATO in a crisis.

U.S. President Donald Trump has repeatedly criticised NATO and told its European members they will have to take over primary responsibility for the conventional defence of the continent.

The U.S. told allies last month of its decision to reduce its contribution to a framework known as the NATO Force Model, which includes a pool of forces that could be activated during a crisis. But it did not publicly disclose any details.

Grynkewich's statement, issued after a meeting of NATO military planners on Wednesday, was the first public indication of what areas the U.S. plans to cut first and where it expects allies to step in.

Manned and unmanned aircraft and naval vessels are two areas where Canada and European allies "can step up now and in the near term - as the United States reduces forces 'sourced' to the NATO Force Model in Europe and refocuses them elsewhere," he said.

"There has been an unhealthy co-dependence in the NATO Force Model on U.S. forces," Grynkewich said in his written statement. "President (Donald) Trump, (Defense) Secretary (Pete) Hegseth and others have been clear that this needs to change, and it will change. The potential reality of simultaneous conflict in multiple theaters demands it."

NATO DOES NOT EXPECT CHANGES TO LEAD TO DEFENCE GAPS

The NATO alliance is under unprecedented strain, with some European countries concerned that Washington may withdraw outright. A major adjustment to the forces the U.S. would make available during wartime will only intensify those concerns.