Agreement but no unanimity over the future of Libyan intervention

The two leaders made it clear that the future of Libya was "without Gaddafi" as they gave a press conference at Lancaster House, in Westminster.

The Prime Minister said it was "time to turn up the heat", while Mr Obama warned that "ultimately this is going to be a slow and steady process".

It was a change of approach from the united front over military action in Iraq, put forward by Tony Blair and George Bush.

However, both current leaders were united in saying there should be no let-up in Nato operations until Col Gaddafi is defeated.

Mr Obama said: "We will continue those operations until Gaddafi's attacks on civilians cease. Time is working against Gaddafi and he must step down from power and leave Libya to the Libyan people."

In a press conference which was meant to show how united they were on major global issues, the two men again described the "special relationship" between the US and UK as "essential" and "unique".

Mr Obama, who has been seen at times as anti-British, went further, noting: "It (the special relationship] has never been stronger."

And the president and the Prime Minister appeared to have put aside their differences on how to deal with the economic crisis. Mr Obama favours investment and an increase in borrowing over the new few years followed by massive cuts, whereas the UK government has already embarked on a programme of deep cuts.

The president acknowledged that different countries had to deal with their problems differently, while Mr Cameron pointed out that the US has a reserve currency which allows it to support debt better.

However, there was confusion over the possible deportation of Scottish computer hacker Gary McKinnon, who broke into Pentagon and Nasa files.

Mr Cameron said he understood "the anger" of McKinnon's family.

Mr Obama added: "We have proceeded through all the processes required under our extradition agreements. It's now in the hands of the British legal system."