A gaffe by US President Joe Biden, who called Ukraine’s Volodymyr Zelenskiy “President Putin”, was “unfortunate”, Anthony Albanese says.

Mr Biden made the slip while introducing the Ukrainian president at the NATO summit in Washington, as he comes under increasing pressure to step down from the upcoming presidential election due to mental fitness concerns.

The mix-up happened just before Mr Biden was set to give a press conference.

Mr Albanese steered clear on whether the US president should step aside from the race but sympathised with Mr Biden, saying it happens.

“Everyone from time to time, I think, has made a slip – it clearly was on his mind who President Zelenskiy is fighting,” the prime minister told Brisbane radio station 4BC on Friday.

“But it certainly is unfortunate.”

Calls have been growing for the Democrats to put up another candidate to run in November’s election against former president Donald Trump, following Mr Biden’s lacklustre performance during a debate in June.

Mr Albanese said whether Mr Biden stepped down or not was a matter for the US, but he did say the president was “on top of his game” when the pair met in Washington in 2023.

“(Biden) chaired a meeting of the entire cabinet … I had a long meeting with him in the Oval Office. We had a couple of dinners, including the official state dinner,” he said.

“He certainly was on top of international affairs, the AUKUS defence arrangements and our relationship, which is so important between Australia and the United States.”

Opposition Leader Peter Dutton said Australia’s relationship with the US would remain strong, regardless of who wins the presidential election.

However, there wasn’t a consensus amongst the Democrats about Mr Biden’s future.

“When you’re speaking privately to Democrats (in Washington), I think they’re sort of equally divided about what they think the president should do,” he told Nine’s Today program on Friday.

“Ultimately, (Biden’s) the one that has to make a call, and we can work with whoever the next president is, whether it’s a second term Biden presidency or President Trump’s elected.”

Mr Dutton has been in Washington as part of the Australian American Leadership Dialogue, a private diplomatic initiative that brings together Australian and American leaders.