WASHINGTON (REUTERS)

After a storm-related ​delay, US President Donald Trump took the stage on the National Mall on Saturday to deliver a campaign-style speech to mark the country's 250th anniversary.

Trump said he would have been willing to wait longer if necessary.

"There's no way we can be deterred," he said, shortly after taking the stage at ⁠11:15pm ET (0315 GMT on Sunday).

Authorities allowed the crowd to return to an open field near the Washington Monument ​where Trump was due to speak, after ordering a weather-related evacuation that forced spectators to shelter in nearby museums ​and government buildings ‌for a few hours.

Visitors had waited hours to get into the ⁠event, contending with ​stepped-up security and temperatures that reached 39 degrees Celsius). The record-breaking heat wave forced the cancellation of several parades and other events in the area.

Past presidents have generally avoided in-person appearances at July ​4 celebrations, and no US president has delivered a July 4 speech on the Mall since 1951. But Trump has blurred the line between official commemoration and campaign-style politics. 

Trump lauded American achievements such as war victories, the lunar landing and the Wright brothers' pioneering flight, as well as the US ​system of government in general. But he also urged Congress to pass stalled legislation that would limit mail ballots and require proof of ​citizenship to register to ‌vote, and cautioned against a rise of communism.

The Trump administration's Freedom 250 group is mainly handling the 250th anniversary and has fenced off much of the 2.4-kilometre National Mall for a "Great American State Fair" featuring attractions such as a Ferris wheel. Freedom 250 says the fair aims to showcase the people and innovations that make ‌the US "the greatest nation on Earth."

Trump opened the event with a rally on June 24.