Washington DC - President Donald Trump has said elections that will decide control of Congress for the rest of his term in the White House are the most important "in our lifetime."

But he cautioned that the sitting president "doesn’t win the midterms," in an apparent move to manage expectations, although he added that "we gave this a very strong shot."

Trump also again rounded on his Democratic opponents, branding them extremists and claiming the party had "nominated the most extreme and dangerous slate of candidates in American history."

The president dedicated a large portion of his final pitch to voters ahead of Tuesday’s elections talking about building projects in Washington, DC, including the troubled renovation of the Lincoln Memorial Reflecting Pool, which he has consistently blamed on vandals although this claim is not supported by his own administration.

US politics Democrats, Trump to hold final rallies before midterms as Republicans face prospect of losing Congress

He joked that "serious thought" was being given to renaming the monument after himself.

He also outlined his plans for building a triumphal arch, that he said would be "more beautiful" than the Arc de Triomphe in Paris, but which has already sparked legal challenges.

Millions of voters head to the polls on November 3 for the hotly contested congressional races, which are being seen as a referendum on the president’s record.

Many people have already cast their ballot in the midterms, which are the most expensive in US history.

While the Democrats have been tipped to retake the House of Representatives from the Republicans, the fight for the Senate remains on a knife's edge.

JD Vance White House feels "pretty good" about deal with Iran as Trump says "it could happen!"

The challengers are expected to benefit from voter discontent over the cost of living and high energy prices fueled by the Iran war, which Trump launched with Israel earlier this year.

The Democrats have faced their own challenges during the campaign with internal divisions, underlined by a public fallout in the Michigan Senate race.

If the party were to gain one or both chambers, it would be able to block legislation and launch investigations into the conduct of Trump’s White House.

However, the president would still have executive authority in key areas and the power of veto, which could frustrate his opponents’ efforts on Capitol Hill.

Speaking at the reopening of the Reflecting Pool, Trump said: "As you know, this is the last day before the midterm elections, the most important midterm I believe in our lifetime."

He added: "The Democrat Party has nominated the most extreme and dangerous slate of candidates in American history."

But he went on: "Usually, whoever the sitting president is, Republican or Democrat, good or bad, good president, great president. For some reason, the sitting president doesn’t win the midterms. But we gave this a very strong shot."

Responding on X, Senate Democratic leader Chuck Schumer said: "Donald Trump’s pathetic closing message as his illegal war rages, his corruption mounts, and the inflation he caused persists."

Earlier, Trump had said he would not hesitate to give pardons to those around him to protect them from potential criminal liability, if the Democrats were to take control of at least one chamber of Congress.

He told a New York Post podcast: "I would if I needed to, sure," adding, "I would not even think about – I’d do it."

Trump pointed to the amnesties granted by former President Joe Biden to family members, administration officials, and politicians, including those who investigated the January 6 attack on the US Capitol in 2021.

The outcome of the elections will influence the debate and party strategies in the run-up to the 2028 presidential race.