President Trump has reportedly questioned the mental fitness of his presumptive Democratic opponent, former Vice President Joe Biden, in recent days and suggested that Biden would fail a simple cognitive test administered to Trump in 2018.

The Washington Post reported Tuesday that the president recently made comments to several White House aides hinting that he did not believe Biden would pass the cognitive exam administered by his White House physician in two years ago as part of an annual physical.

The president has repeatedly referred to Biden with the pejorative nickname "Sleepy Joe" and suggested that the former vice president has low intelligence.

"He’s not as smart as Bernie, and he’s not as quick," he said in an interview with a Boston radio station last month, referring to former presidential candidate Sen. Bernie Sanders (I-Vt.).

The Biden campaign did not immediately return a request for comment.

“For someone so obsessed with appearing strong, Donald Trump shows us every day just how weak he is,” a Biden campaign press secretary said in a statement Monday, adding: “Donald Trump doesn’t care about the health or economic prosperity of the American people. He only cares about himself.”

Trump has also faced criticism of his own physical and mental wellbeing in recent weeks. The conservative anti-Trump group Lincoln Project has repeatedly run ads mocking the president, including for his speaking and walking style, in recent weeks.

"He’s shaky, weak, trouble speaking, trouble walking," one ad released by the group last week says in narration.