Trump launches outburst against 'ungrateful' traitor Chelsea Manning

US President Donald Trump has hit out at the decision to release Wikileaks whistleblower Chelsea Manning, describing the former soldier as an "ungrateful traitor".

Trump was responding to an article published by Manning in the Guardian newspaper, in which she suggested that his predecessor Barack Obama was a weak leader.

Manning's sentence was commuted shortly before the end of Obama's second term earlier this month, allowing her to be released in May even though her original sentence was 35 years.

"Ungrateful TRAITOR Chelsea Manning, who should never have been released from prison, is now calling President Obama a weak leader. Terrible!" Trump tweeted on Thursday morning.

The article published on Thursday in the daily newspaper was a commentary on Obama's two terms at the helm of the US government, in which she is critical of the former President's actions on diversity, but reserves most of her criticism for his opponents for failing to meet his compromises.

"The one simple lesson to draw from President Obama's legacy: do not start off with a compromise. They won't meet you in the middle. Instead, what we need is an unapologetic progressive leader," Manning wrote.

Manning was sentenced after being found to have supplied Julian Assange's whistleblowing site with thousands of files from the US military, revealing malpractice during the Iraq and Afghanistan wars.