US senator and former presidential hopeful Mitt Romney has called for Donald Trump and Joe Biden to "stand aside" and make room for a new generation of politicians.
He made the remarks while speaking to media about his own plans to retire.
He said he was choosing not run again because it was time "for a new generation of leaders".
Mr Romney, 76, has had a 20-year career in US politics, including a stint as governor of Massachusetts.
In recent years, the prominent Republican has become a vocal critic of both Mr Biden and Mr Trump.
He will remain in office until the end of his senate term in January 2025.
In a video announcing his choice to not run again, posted to social media on Wednesday afternoon, Mr Romney suggested that age played a role in his decision.
"At the end of another term I'd be in my mid-80s. Frankly, it's time for a new generation of leaders," he said. "While I'm not running for re-election, I'm not retiring from the fight".
He later told reporters that he plans to get young people to join the Republican party, run for office and vote, and that both parties would be "well served" by being able to choose candidates from younger generations.
In response to a question from the BBC, Mr Romney also said that it would be a "great thing" for both President Biden and Mr Trump to step aside so both parties can pick "someone in the next generation".
Mr Biden, 80, and Mr Trump, 77, are the frontrunners for the 2024 presidential race for the Democrats and Republicans, respectively.
Mr Romney also contrasted himself with some fellow Republicans, arguing that he represents a "small" and "wise" part of the party focused on policy goals.
Republican lawmakers who support Mr Trump, he said, are focused on "getting even" and settling scores for perceived grievances.
Mr Romney was the Republican nominee for president in 2012 but ultimately lost to incumbent Barack Obama.
Six years later, he was elected as one of Utah's two senators. He had previously launched an unsuccessful bid to become the Republican nominee in 2008 and served as Massachusetts' governor between 2003 and 2007.
In 2020, he voted to convict Mr Trump during his first impeachment trial, becoming the first senator to ever vote to convict a member of his own party. He was the only Republican to do so.
The following year, he again voted to convict the former president during his second impeachment trial in the wake of the 6 January 2021 riot at the US Capitol.
Since then Mr Romney has been an enemy of the former president. Mr Trump celebrated the announcement, writing in an all-capital-letters post on Truth Social that Mr Romney "did not serve with distinction" and called his retirement "fantastic news".
In Mr Romney's absence, his Senate seat will almost certainly go to one of several Trump-supporting candidates who are seen as possible contenders.