Trump saluted after walking onto a huge stage in front of the White House, with two huge tanks parked nearby, while a 21-gun salute rang out and the national anthem played.

The parade, officially marking the 250th anniversary of the US Army but also coinciding with Trump's birthday, was set to feature tanks, a flyover and nearly 7,000 troops marching past.

But the deep political divisions in the United States were underscored as "No Kings" demonstrators earlier took to the streets in cities including New York, Los Angeles, Washington, Houston and Atlanta.

The killing of a Democratic lawmaker and her husband in Minnesota also cast a pall over the parade.

Trump was quick to condemn the attacks outside Minneapolis in which former state speaker Melissa Hortman died along with her husband, while another state lawmaker and his wife were hospitalized with gunshot wounds.

The "No Kings" demonstrators were protesting what they call Trump's dictatorial overreach, and in particular what they call the strongman symbolism of the biggest parade in Washington for decades.

"I think it's disgusting," protester Sarah Hargrave, 42, told AFP at a protest in the Washington suburb of Bethesda, describing Trump's parade as a "display of authoritarianism."

Republican Trump, who has begun his second term by pushing presidential powers to unprecedented levels, boasted earlier on his Truth Social network that it was a "big day for America!!!"

He added that Russian strongman Vladimir Putin, for whom he has repeatedly expressed admiration, had "very nicely" called him to wish him a happy birthday.

The two leaders also agreed on the need for an end to the Iran-Israel conflict -- a war in which US forces are aiding Israel to shoot down Tehran's missiles.

- Political violence -

The "No Kings" protest organizers expected millions of people to take part in 1,500 cities in the rest of the country.

Some protesters targeted Trump's Mar-a-Lago estate in Palm Beach, Florida -- while a small group even gathered in Paris.

Thousands turned out in Los Angeles to protest Trump's deployment of troops in the country's second-largest city following clashes sparked by immigration raids.

The White House dismissed the rallies.

"The so-called No Kings protests have been a complete and utter failure with minuscule attendance," White House Communications Director Steven Cheung said in a post on X, despite photos of large crowds in a number of cities.

Trump had promised to use "very big force" if protesters attempt to disrupt the army parade in Washington.

But disruption could also come from thunderstorms forecast to hit Washington as the parade continues.

Trump put on a brave face, saying on Truth Social: "Our great military parade is on, rain or shine. Remember, a rainy day parade brings good luck. I'll see you all in DC."

- $45 million -

The military parade is the biggest in Washington since the end of the Gulf War in 1991, estimated by the army to cost up to $45 million.

Soldiers will wear uniforms dating back through US history to its independence from Britain as they march past landmarks including the Washington Monument to end up at the White House.

Trump has been obsessed with having a parade since his first term as president when he attended France's annual Bastille Day parade in Paris at the invitation of President Emmanuel Macron.

Critics have accused Trump of acting like autocrats in Moscow or Pyongyang.

California's Governor Gavin Newsom, who slammed Trump for sending National Guard troops into Los Angeles without his consent, called it a "vulgar display of weakness."