David Cameron has raised the prospect that computer hacker Gary McKinnon could serve some of any US-imposed sentence in a British jail after raising the issue with US President Barack Obama at the White House.
He said it was "one potential outcome" of senior-level talks between Britain and the US over the fate of Mr McKinnon, who broke into top secret US military computers.
The Prime Minister said that the Government had been working with the US ambassador on options "where perhaps some of the (sentence) if there is a prison sentence - is served in a British prison".
"That is one potential outcome and I'll be working very hard to make sure that these things are discussed between the two governments and if we can reach a settlement then all to the good. I don't want to make a prediction because there are many difficult issues that have to be worked through."
Both Mr Cameron and Deputy Prime Minister Nick Clegg have publicly condemned plans to extradite Mr McKinnon to the US - where he faces up to 60 years in jail.
Last year Mr Cameron said that if Mr McKinnon, 43, had questions to answer there was "a clear argument to be made that he should answer them in a British court".
Authorities in the US want Mr McKinnon to stand trial for hacking into top secret military computers.
Mr McKinnon, who suffers from Asperger's syndrome and comes from Wood Green, north London, says he was looking for evidence of UFOs.