Kevin McCarthy says Biden's biggest problem is his age

• Kevin McCarthy said President Joe Biden has an age problem.
• "There is a real concern here," McCarthy said as he remarked on Biden's ability to effectively lead.

Former House Speaker Kevin McCarthy said Tuesday during a CNBC interview he had "a real concern" about President Joe Biden's ability to effectively interact with foreign leaders, shining another spotlight on the debate around the president's age ahead of the 2024 election.

"Biden can't solve his problem. His problem is age," McCarthy said during a discussion on CNBC's "Squawk Box."

McCarthy, who last December retired from the House following his ouster as speaker in October, painted a less-than-stellar picture of Biden's presidential abilities at the White House.

"I have personally been in situations where I walked out not telling the press what has transpired but was deeply upset as an American of what I saw just transpire," the California Republican said. "Just hoping that he doesn't have any interaction with another world leader with the interaction I just had with him."

"So yes, there is a real concern here and I think that would be on top of everything else," he added.

As Biden has ramped up his reelection campaign, he's had to contend with questions about his mental acuity given that he'd be 82 years old at the start of a second term and 86 at the end of said term.

The questions were amplified after a special counsel report on Biden's handling of classified documents didn't recommend charges against him but described his memory as "hazy" and "poor." After the report was released, Biden firmly pushed back against that characterization in a fiery speech at the White House.

Vice President Kamala Harris leaped to the president's defense, blasting the special counsel's claims regarding Biden's memory as "inaccurate and inappropriate."

Republican Sen. Mitt Romney of Utah earlier this month told The Huffington Post that while age would be a "huge issue" in the expected rematch between Biden and former President Donald Trump, he hadn't witnessed an overly concerning situation regarding the president's mental acuity.

"I've worked with the president, and I haven't seen anything that's abnormal before," Romney, who was a key player in crafting the 2021 bipartisan infrastructure bill, told the news outlet.

Trump's age has also been raised as an issue, as the 77-year-old has sometimes made rambling remarks on policy issues and mixed up the names of prominent figures.

Former South Carolina Gov. Nikki Haley, Trump's remaining major Republican primary opponent, has said that American voters want to move beyond a Biden-Trump rematch, pointing to her candidacy as one that represents a new generation of GOP leadership.

But so far, Republican voters remain solidly behind Trump, as he's won every major statewide primary or caucus since January.