WASHINGTON • Tanks in the heart of Washington, fighter jets screaming overhead, and a speech from the Lincoln Memorial: US President Donald Trump promised the "show of a lifetime" yesterday as he turned the Fourth of July into a personal prime-time extravaganza.

The commander-in-chief and erstwhile Manhattan showman planned to tear up another norm, critics said, by hijacking traditionally non-partisan Independence Day as he seeks re-election.

"Our July 4th Salute to America at the Lincoln Memorial is looking to be really big. It will be the show of a lifetime!" Mr Trump tweeted on Wednesday.

"We have the greatest economy anywhere in the world. We have the greatest military anywhere in the world. Not bad!" he added.

Vice-President Mike Pence also chimed in. "The #SalutetoAmerica at Lincoln Memorial tomorrow night will be a great show and an amazing display of our country's wonderful military!" he tweeted on Wednesday.

Usually, said associate professor Rich Hanley - a media and popular culture expert at Quinnipiac University - July 4 works as a kind of national ceasefire.

"It's a day when people can set aside their polarised differences... and raise the flag without entering into political discussions," he said. "Then on the 5th they go back to normal."

But this year, the familiar script has been given a rewrite. At around 6.30pm yesterday, Mr Trump was to take to the hallowed steps of the Lincoln Memorial for an unprecedented "Salute to America" event that was set to include a televised address, military hardware and a giant fireworks display.

Members of the nation's top military brass were to have a front-row seat. The modified Boeing 747 used as Air Force One was set to fly over, as were noisy, powerful warplanes such as F-35s and jets from the Navy's Blue Angels air show team.

A handful of tanks and Bradley fighting vehicles were stationed near the Lincoln Memorial, although the enormous M1 Abrams tanks were not expected to roll, as their tracks would likely tear up the city's streets.

However, the centre of attention was not the weapons, or the nearly million dollars' worth of fireworks - a donation from two big manufacturers. Rather, it was Mr Trump himself. "Your favourite President, me!" he tweeted when announcing the show.

July 4 is a unique holiday in that it is hyper-patriotic but free from the usual Republican-Democratic fighting and it is far more civic than military in nature.

Inserting such a high-profile presidential address into the festivities risks changing that, given that the polarising Mr Trump is supported by just over 40 per cent of the country ahead of his re-election bid next year and fervently opposed by much of the remaining electorate.

Mr Trump's "ego is so large that he's holding this Fourth of July campaign rally in a desperate cry for attention, and everyone knows it", Democratic Senator Chuck Schumer wrote on Twitter.

Counter-protesters planned to bring their own kind of political fireworks to the National Mall, the grassy park running three kilometres from the Lincoln Memorial to the Capitol.

Leftist organisation Code Pink was deploying its "Baby Trump" blimp, a large inflated doll depicting the President in diapers.

But the National Park Service denied permission to fill the inflatable with helium, so the blimp will stay on the ground.

Many were up in arms about what the celebration was going to cost. The White House has so far refused to say.

"Instead of addressing something like veteran homelessness, he's spending it on boosting his ego with a parade that's fundamentally about him," said Democratic presidential hopeful Julian Castro. "What a waste of money."

A former reality TV star, Mr Trump tapped his considerable showmanship skills ahead of the event. Just being up on the Lincoln Memorial is a guarantee of unbeatable pictures. The statue honouring civil war president Abraham Lincoln is famous as the location for Martin Luther King Jr's epic 1963 "I have a dream" speech.

As he prepared for the big day, Mr Trump downplayed the issue of cost. "The cost of our great Salute to America tomorrow will be very little compared to what it is worth," he wrote.

AGENCE FRANCE-PRESSE