Donald Trump has said he does not support an age limit for running for president – but he does support a mental competency test.

Trump, 77, told NBC News in an interview airing on Sunday that he doesn’t believe age matters, but cognitive function does in a dig at Biden’s perceived mental decline.

‘I don’t think Biden’s too old,’ he said. ‘But I think he’s incompetent, and that’s a bigger problem.’

But Trump made his own gaffe earlier on Saturday during an appearance in Washington DC. He said Biden would lead the US into World War Two – which concluded in 1945 – and appeared to say he was beating Barack Obama in the polls.

Obama served as president for two terms between 2009 and 2017 and cannot be re-elected. 

Joe Biden, 80, is the oldest person ever elected president, and his age is worrying many voters across the political spectrum. A poll last month reveals 77 percent of Americans – including 69 percent of Democrats – think Biden is too old for a second term. 

Donald Trump told NBC News, in an interview to be aired on Sunday, that he supports a mental competency test for anyone wanting to be president

Trump, 77, said Joe Biden, 80, was not too old – but just ‘incompetent’

If Biden reclaims the White House, he would be 82 years old at the beginning of his second term in January 2025.

If Trump wins, he would be 78 ? the same age that Biden was when he began his first term in 2021. 

Trump said many successful political figures in history were older than him.

‘You know, some of the greatest world leaders have been in their 80s,’ he said.

The 77-year-old GOP candidate added: ‘I’m not anywhere very near 80, by the way.’

And he said the 10-minute mental evaluation he took while president, designed to screen for mild cognitive impairment or early dementia, should be compulsory.

‘You know, I took a test two years ago, three years ago,’ he told NBC’s Kristen Welker.

‘And as the doctors said — and it was in front of doctors and a whole big deal at Walter Reed [hospital], which is an incredible place,’ he added. 

‘And I aced it. I get everything right,’ the former president said. ‘I’m all for testing. I frankly think testing would be a good thing.’

‘A lot of people say it’s not constitutional to do it. But I would be for testing, to test to make sure everyone’s just fine.

‘But a lot of people say that can’t happen because of the Constitution.’

Trump said in an interview with former Fox News host Megyn Kelly released last week that Biden isn’t too old, but just ‘grossly incompetent,‘ and should not be elected for another four-year term. 

Biden, seen leaving church in Delaware on Saturday, has been dogged by questions about whether he is too old to run for a second term

In March, a Pew report found that most world leaders – 35 percent – are aged in their 60s, with the media age of 62.

Chile has the youngest head of government: Gabriel Boric is 37. Paul Biya of Cameroon is 90 – the only world leader in their 90s.

Roughly a quarter are in their 50s, while 18 percent each are in their 40s or 70s.

Biden is among the 5 percent of leaders who are in their 80s.

Biden and Trump are both out of step with the average American, who is aged 38.

Biden’s age is of more concern to voters than is Trump’s, according to two recent polls.

Both the Associated Press and the Wall Street Journal have found that three-quarters of Americans view Biden as too old to be president, yet only about half say the same of Trump.

Biden is not helped by his repeated gaffes.

Joe Biden is seen on Monday, the 22nd anniversary of 9/11, speaking to troops in Anchorage, Alaska. He is the first president not to spend the anniversary at the site of one of the three plane crashes

Biden (center) is seen visiting Ground Zero on September 20, 2001 with fellow senators Ted Kennedy (left) and Barbara Mikulski (center, in poncho). He was in Washington DC on September 12, 2001

On Thursday, the White House had to edit a transcript of a speech after he declared he had reduced unemployment among ‘African Americans and Hispanic workers and veterans, you know, the workers without high school diplomas.’

He was supposed to say that he had reduced unemployment among black people, Hispanics, veterans, and those without diplomas.

On Monday, the anniversary of 9/11, he told troops in Alaska that he was in New York the day after the terror attacks.

‘Ground Zero in New York – I remember standing there the next day and looking at the building,’ he said.

Yet Biden was in Washington DC – something he notes in his 2017 autobiography. C-Span footage shows him speaking in Congress on September 12, 2001.