Edward Snowden has asked Barack Obama to grant Chelsea Manning clemency over himself, despite having spent months campaigning to get a presidential pardon.

'Mr President, if you grant only one act of clemency as you exit the White House, please: free Chelsea Manning. You alone can save her life,' the former intelligence analyst wrote on Twitter Wednesday.

Manning is currently serving a 35-year sentence at Fort Leavenworth, Kansas, for disclosing classified and sensitive information to Wikileaks. She has attempted suicide twice since being sentenced in 2013 and has repeatedly asked for better treatment for her gender dysphoria.

Edward Snowden (left) asked President Barack Obama Wednesday to grant Chelsea Manning (right) clemency over himself. Manning is serving 35 years at Fort Leavenworth, Kansas

The former US Army soldier is on a short list for a possible commutation, a Justice Department source said Wednesday. Meanwhile, Snowden has been charged with espionage and has been living in exile in Russia since leaking classified documents related to US and UK surveillance in 2013.

Snowden's plea comes the day before Wikileaks co-founder Julian Assange said he would accept extradition to the US if Obama grants Manning clemency.

Manning has asked Obama to grant her time served, while Snowden has been asking for a pardon for himself. Both are forms of clemency that can be awarded by the president.

Lawyers have denounced Manning's detention conditions. The former soldier said she was kept in solitary confinement for nearly a year and hasn't been allowed to grow her hair longer than what is required for male inmates.

'Hair is the most important signifier of femininity in American society, and it is especially important to me as a person confined in an all-male environment, so not being given access to this, while receiving other treatment, has been a never-ending nightmare,' Manning wrote in a plea for clemency.

The former US intelligence analyst pleaded Obama to free Manning if it were the only act of clemency he granted during his final days at the White House

Manning (pictured) has attempted suicide twice behind bars, saying she was kept in solitary confinement for nearly a year and asking for better treatment for gender dysphoria

Manning's aunt told NBC News that a commutation in the last days of Obama's presidency might be her last hope for the near future.

'I have more hope right now than I have the entire time since she was sentenced,' Deborah Manning told the network. 'I do think it's the last hope for a while.'

The comment came as a Justice Department source told NBC News that Manning was on a short list to receive a possible commutation.

Snowden meanwhile has asked for a presidential pardon since November.

'Yes, there are laws on the books that say one thing, but that is perhaps why the pardon power exists – for the exceptions, for the things that may seem unlawful in letters on a page but when we look at them morally, when we look at them ethically, when we look at the results, it seems these were necessary things, these were vital things,' he previously told The Guardian.

The former intelligence analyst however put his own case aside while making a plea for Manning on Wednesday.

Assange too sided with Manning over himself when he said he would agree to face extradition to the US if Obama granted the former soldier clemency.

'If Obama grants Manning clemency Assange will agree to US extradition despite clear unconstitutionality of DoJ case,' Wikileaks tweeted Thursday.

Obama has made the biggest use of presidential clemency in modern history. He granted 153 commutations and 78 pardons in December, meaning he has showed mercy to 1,324 individuals so far.