Tony Blair has asked US President George Bush to send home UK detainees from the Guantanamo Bay prison camp.
Moazzam Begg and Feroz Abbasi are among the four detainees
His request is included in court papers outlining the UK government's defence against action by two of the detainees.
Feroz Abbasi and Martin Mubanga want a court order requiring UK authorities to make a formal demand for their return.
Irish Prime Minister Bertie Ahern said he also raised the treatment of detainees in Cuba with Mr Bush during an EU summit on Saturday.
The papers submitted to the High Court say the judicial review sought by the two detainees is not necessary, because the government has already requested their return.
They read: "The UK government is continuing to seek the return of the four remaining detainees and the prime minister has made a direct request to President Bush to that effect."
Talks 'at many levels'
A Downing Street spokesman refused to say when Mr Blair raised Guantanamo with President Bush.
He said talks about the four British detainees had taken place at many levels of the British and American governments.
"The negotiations have been led by the attorney general, but it's something the PM has raised with the president and we've said that in the past.
"Discussions have been ongoing with the US for a long time and we continue to work to resolve the situation."
But Louise Christian, a lawyer for two of the four Britons being held at Guantanamo Bay, said she believed the direct approach by Mr Blair to President Bush was made in the last month.
"It's an important new development, but the important thing now is the response," she said.
"We will see whether the British government actually has got the clout with the US government to get its citizens back out of this place.
"I think that Tony Blair should be able to use his authority and influence
with George Bush to get the whole of Guantanamo Bay closed down, but if he can't
do that, at least he must fulfil his obligations towards British citizens," Ms Christian added.
Details of the request follow concerns over planned military tribunals for the terror suspects held at Guantanamo Bay.
The UK government has always voiced reservations over the trial plans.
In a speech on Friday, attorney general Lord Goldsmith argued there could be "no compromise" on certain principles and the US tribunals would not offer a fair trial.
BBC correspondent Jon Manel said the papers had to be seen in the context of negotiations over British citizens in the Guantanamo Bay camp.
But he added: "What this shows is how negotiations have been evolving.
"We now know that the government is very disillusioned with the military commissions and has requested that the detainees be returned."
President Bush announced plans for the military commissions to try 600 detainees at Camp Delta last July.
Britons Feroz Abbasi from Croydon, south London, and Moazzam Begg, from Birmingham, were on the initial list of six to be tried under the controversial set-up.
But they have now been taken off the list while discussions continue between the US and UK about the future of all the British detainees.
Five other Britons were returned to Britain in March and were quickly freed without charge.