A Briton accused of hacking into American military and NASA computers could serve part of any US-imposed sentence in Britain, Prime Minister David Cameron said Wednesday.

Gary McKinnon, 43, who suffers from Asperger's Syndrome, a form of autism, faces extradition to the United States -- something Cameron has publicly condemned.

He could spend life in prison if convicted by a US court of gaining access to 97 computers in 2001 and 2002 in the aftermath of the September 11, 2001 attacks.

McKinnon says he was only looking for evidence of unidentified flying objects when he hacked into the US Navy and NASA space agency computers.

His case was raised at the White House during talks Tuesday between Cameron and US President Barack Obama, in Cameron's first visit to Washington since becoming prime minister in May.

Cameron told BBC radio that his government had been working with the US ambassador on options "where perhaps some of the -- 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," he said.

"I don't want to make a prediction because there are many difficult issues that have to be worked through."

At a White House press conference Tuesday, Obama said he wanted the issue resolved "in a way that underscores the seriousness of the issue, but also underscores the fact that we work together, we can find an appropriate solution".

Speaking alongside the president, Cameron said he did not want to prejudice discussions between Washington and London.

"We completely understand that Gary McKinnon stands accused of a very important and significant crime in terms of hacking into vital databases and nobody denies that is an important crime that has to be considered," he said.

"I have had conversations with the US ambassador as well as raising it today with the president about this issue, and I hope a way through can be found."