The tweet on Sharp's account reads: "@beezan Obama said on TV with Cameron, Happy to let UK make extradition decision and U.S will abide by it. #FreeGary".
The US government has accused Gary McKinnon of hacking 73,000 federal and military computers and causing some $800,000 in damage. If convicted, McKinnon, who suffers from an autistic condition called Asperger's syndrome, faces up to 60 years in a US jail. McKinnon admits that he hacked into Pentagon systems in 1999, but says he was searching for evidence of UFOs.
He has been under threat of extradition. As recently as two weeks ago, US authorities insisted that self-confessed hacker face a US court, despite ongoing efforts to have the trial in the UK.
Sharp and McKinnon were hoping for a breakthrough in his case during President Obama's visit to the UK. Obama promised to find an "appropriate solution" last year.
But Attorney General Eric Holder has vowed to "take all necessary steps" to have McKinnon extradited and "held accountable for the crimes that he committed", according to the UK's Daily Mail earlier this month.
This story was first published by Computer Weekly