Julian Assange's wife said on Thursday it was a "good sign" that US President Joe Biden was "considering" dropping the WikiLeaks founder's prosecution, five years on from his arrest and detention.

"It looks like things could be moving in the right direction," Stella Assange told the BBC.

Australia's parliament passed a motion in February with the prime minister's support calling for an end to the legal saga surrounding Assange, an Australian who has been held in Britain since 2019 while fighting extradition to the United States.

"We're considering it," Biden replied at the White House when asked by a reporter if he had a response to Australia's request.

"It's a good sign. The prime minister of Australia (Anthony Albanese) overnight said that he is optimistic," Stella Assange told the BBC.

Her husband has now spent five years at the high-security Belmarsh Prison in southeast London.

The 52-year-old Assange is currently waiting to learn if he can make a last-ditch appeal against extradition to the United States, after a UK court last month delayed a decision on his case. It is now expected on May 20.

The US indicted Assange multiple times between 2018 and 2020 but Biden has faced persistent domestic and international pressure to drop the case filed under his predecessor, Donald Trump.

Washington alleges that Assange and others at WikiLeaks recruited and agreed with hackers to conduct "one of the largest compromises of classified information" in US history.

Before going to prison, Assange spent seven years holed up in Ecuador's London embassy to avoid extradition to Sweden, where he faced accusations of sexual assault which were later dropped.

He was eventually arrested on April 11, 2019, when Ecuador revoked his asylum.

His supporters marked the anniversary by protesting outside the Australian High Commission in central London, holding banners reading "Free Assange".

Stella Assange said on Thursday that her husband was "extremely unwell" and "stressed obviously because he could be extradited to the United States to face 175 years in prison.

"I hope Joe Biden really just drops this case now as the entire human rights community and press freedom community is asking him to do," she added.