The US President is hosting a rally Wednesday on the National Mall in Washington. He has said it will be replete with a military flyover by stealth bombers, military bands, singer Lee Greenwood of "God Bless the USA" fame and a speech by Trump.

It comes as Trump works to convince Americans ahead of critical November midterm elections that he's put the unpopular Iran war in the rearview mirror, with oil prices easing as the Strait of Hormuz has started to reopen in the wake of an interim deal to end the war with Tehran.

The rally is designed to kick off weeks of celebrations about America and its 1776 founding as part of "The Great American State Fair" on the mall, the national park that stretches from the US Capitol to the Lincoln Memorial.

But Trump's appearance onstage was only announced after several musicians - including Young MC, Martina McBride and the Commodores - cancelled their concerts because of concerns the event had become politicised. The president stepped into the void as he hyped his own ability to command a crowd.

"I am thinking about bringing the Number One Attraction anywhere in the World, the man who gets much larger audiences than Elvis in his prime, and he does so without a guitar, the man who loves our Country more than anyone else, and the man who some say is the Greatest President in History," Trump posted on social media about his plan to be the event's headliner.