US Secretary of State Marco Rubio has reassured allies that Donald Trump is not anti-NATO and that the country will remain in the alliance, but he's also asking his counterparts to make sacrifices and raise defence spending to 5%.

The secretary of state’s trip comes amid an abrupt shift in relations between the United States and Europe after close cooperation during the Biden era.

Rubio arrives in Brussels on Thursday for two days of meetings with his NATO counterparts and European officials, and he can expect to be confronted with questions about the future U.S. role in the alliance. With him on the trip will be newly confirmed U.S. ambassador to NATO Matt Whitaker.