More than 100 MPs are calling on Barack Obama to block the extradition of a Suffolk man accused of hacking into US government computer networks.
Lauri Love, from Stradishall near Newmarket, is alleged to have stolen significant amounts of data from US agencies including the federal Reserve, Nasa and the FBI. He could face up to 99 years in prison if found guilty.
105 cross-party backbenchers have signed a letter to the US President leader, stressing their "deep concern for the safety" Mr Love, who has Asperger's Syndrome.
The letter points out that the UK has prosecuted at least 12 people who have hacked US-based computer systems.
Mr Love, who also suffers from depression and severe eczema, has said a jail term in the US would cause his health to deteriorate and would lead to a mental breakdown or suicide.
"We are very happy for this young man to be tried in our courts and to see justice served here," Autism Commission chair Barry Sheerman MP said.
"But his mental health is so precious that we feel he would self-harm if he was sent back to the United States."