Donald Trump is trying to unify the Republican Party by endorsing House Speaker Paul Ryan.

The endorsement came during a rally in Ryan's home state of Wisconsin.

The presidential nominee also endorsed Arizona Senator John McCain, praising him for his service to the country "in uniform and in public office," and he also endorsed New Hampshire Senator Kelly Ayotte, calling her a "rising star" in the party.

Trump has been facing criticism for not endorsing candidates that supported him. (Metro News Inc)