Donald Trump spent a large part of a meandering speech on the eve of crunch US midterm elections talking about grass and algae.

The US president dedicated a large portion of his final pitch to voters ahead of Tuesday’s elections talking about 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.

Speaking at the reopening of the reflecting pool in Washington DC, Trump mentioned the word “grass” roughly 20 times as he lauded his administration’s effort’s to clean up beauty spots in the capital.

At one point he held up a photo of the reflecting pool after its water had turned green. “That’s not grass, that’s algae,” Trump said.

“The pool is now better and more beautiful than it’s ever been before, and we’re very proud of it,” he added.

The speech, which comes as voters struggle with high fuel prices on the back of Trump’s war on Iran, was described by one UK commentator as “one of the most bizarre midterm-eve presidential appearances ever”.

Sky News US Correspondent Mark Stone said: “His meandering speech, full of demonstrably false statements, suggests that his communications team have totally lost control of the messaging.”

Trump eventually turned to the subject of the midterms, saying the 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 Democrat opponents, branding them extremists and claiming the party had “nominated the most extreme and dangerous slate of candidates in American history”.

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

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

A number of state governorships are also being contested, including in California, where the Republican candidate is Steve Hilton, a former top aide to David Cameron.

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

The challengers are expected to benefit from voter discontent over the cost of living and high energy prices.

The president has held rallies in traditional Republican strongholds in a bid to shore up support and boost turnout, and promised every adult US citizen $5,000 if his party kept control of both the House and Senate.

But 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 was 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.

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.”