Washington will transfer leadership of NATO's Naples command, which focuses on the alliance's south, to Italy and leadership of its Norfolk command in Virginia, focusing on the alliance's north, to Britain.

The United States will meanwhile take over the command of NATO's maritime forces, based in the United Kingdom.

The changes, first reported by French outlet La Lettre, will likely take months to be implemented, two NATO diplomats told AFP, speaking on condition of anonymity.

"It's a good sign of burden shifting in practice," a diplomat said.

The shuffling of NATO command positions comes as Washington has said it could reduce its defence presence in Europe to focus on other threats like China.

But military superpower Washington will still remain central as it will have control of NATO's core air, land and sea commands and retain the top position of Supreme Allied Commander Europe.

European countries have already ramped up military budgets in the face of Russia's invasion of Ukraine and last year agreed to hike NATO's defence spending target.

Trump has rattled faith in the reliability of the United States and last month plunged the alliance into crisis by making claims on Greenland.

But US NATO ambassador Matthew Whitaker separately on Monday insisted that the US leader was looking to strengthen, rather than "dismantle", NATO by making Europe step up.

"We're trying to make NATO stronger, not to withdraw or reject NATO, but make it work like it was intended as an alliance of 32 strong and capable allies," Whitaker said.