Former President Donald Trump, the oldest candidate in the 2024 GOP presidential field, said there should not be an age limit for the presidency but expressed support for requiring mental competency tests for candidates.

"I'm all for the tests," Trump told NBC's Kristen Welker in an interview clip that aired Saturday, citing a cognitive test he took in 2020 at Walter Reed National Military Medical Center. "I aced it. I get everything right."

But the former president, 77, cast doubt on the practicality of requiring such a test, adding, "A lot of people say it's not constitutional to do it."

Trump's comments come as he considerably leads the Republican presidential pool to face President Joe Biden -- who is 80 -- in 2024.

When asked if there is a need for a new generation to take the helm, Trump said, "It's always time for a new generation."

But, he added, "Some of the greatest world leaders have been in their 80s," though the 77-year-old quickly clarified that he's "not anywhere very near 80, by the way."

The ages of the incumbent and the GOP front-runner have raised questions about whether they are fit for office, and other presidential candidates have used the issue to argue that they will not be effective leaders.

But Trump said the problem with his predecessor is "bigger" than his age.

"I don't think Biden is too old, but I think he is incompetent," Trump said. "And that's a bigger problem."

Biden, who would be 82 at the start of his next term if reelected, has also shrugged off concerns about his age in recent months. When asked why an 82-year-old would be the best fit for president, Biden told MSNBC in May that he has "acquired a hell of a lot of wisdom."

"I'm more experienced than anybody (who's) ever run for the office," he said, adding that he thinks he's proven himself to be effective.

However, a recent CNN poll showed that roughly three-quarters of Americans say they're seriously concerned that Biden's age might negatively affect his current level of physical and mental competence and his ability to serve out another term if reelected.

Trump's full interview with NBC's Welker will air Sunday morning on "Meet the Press."