Donald Trump selected US Senator J.D. Vance on Monday to serve as his vice presidential running mate, as the Republican Party officially nominated the former president as its 2024 presidential nominee at the start of the party's national convention in Milwaukee.

"As Vice President, J.D. will continue to fight for our Constitution, stand with our Troops, and will do everything he can to help me MAKE AMERICA GREAT AGAIN," Trump wrote on his Truth Social platform.

The four-day convention opened in downtown Milwaukee's Fiserv Forum two days after Trump survived an assassination attempt in Pennsylvania, and hours after he secured a major legal victory when a federal judge dismissed one of Trump's criminal prosecutions.

Trump is due to formally accept the party's nomination in a primetime address on Thursday and will challenge Democratic President Joe Biden in the Nov. 5 election.