Airforce general Alexus Grynkewich was nominated by President Donald Trump and approved by NATO's 32 allies, the US defence department and NATO said in statements.

The appointment -- which now has to be confirmed by the US senate -- comes as Washington has warned it could look to shift forces from Europe to focus on China.

US outlet NBC reported in March that the Trump administration was considering giving up the role of Supreme Allied Commander Europe (SACEUR), which was first held by Dwight D. Eisenhower in the early 1950s.

NATO diplomats played down the prospect of the United States renouncing the post, which they said would signal an effective US withdrawal from the alliance's operations in Europe.

Grynkewich replaces Christopher Cavoli, who has spearheaded Western efforts to support Ukraine in its fight against Russia and bolster NATO's own capacities to ward off Moscow.