The US has offered to return former British residents being held at Guantanamo Bay to the UK, say reports.
Guantanamo Bay has angered human rights groups
The Guardian newspaper quotes leaked documents written by UK officials saying the American government is willing to send the men back.
But the British government said the men did not pose a big enough threat to justify the strict security conditions demanded by the United States.
The Foreign Office says it cannot comment on individual cases.
Nine Britons have already been returned from Guantanamo Bay in the last two years and freed without charge.
But at least nine former UK residents are understood to remain among the detainees.
The Guardian says it has obtained witness statements from the director general of defence and intelligence at the Foreign Office, David Richmond, and the director of counter-terrorism and intelligence at the Home Office, William Nye.
They appear to show the US is willing to return the men to the UK under strict conditions.
Mr Richmond reportedly says: "The British embassy in Washington was told in mid-June 2006 that, during an internal meeting between US officials, the possibility had been floated of asking the UK government to consider taking back all the detainees at Guantanamo who had formerly been resident in the UK."
'All or nothing'
Mr Richmond said details of the meeting had been given informally to the embassy and the government wanted to "clarify the significance of the idea".
UK officials reportedly met American officials from the State and Defense Departments, as well as the National Security Council on 27 June.
Mr Richmond said about the meeting: "The US administration would only be willing to engage with the UK government if it sought the release and return of all the detainees who had formally resided in the UK (ie regardless of the quality of their links with the UK), rather than just a subset of the detainees falling in that category."
Mr Nye said the American government wanted a series of measures to stop the former detainees leaving the UK, meeting known extremists or planning, supporting or promoting extremism or violence.
It also wanted to be sure the British authorities would know immediately if they did try to engage in any of those activities.
Mr Nye said: "I am not satisfied it would be proportionate to impose ... the kind of obligations which might be necessary to satisfy the US administration."
He argued the resources needed to meet US demands "could not be justified and would damage the protection of the UK's national security".
It is thought he was worried the measures would take resources away from monitoring more dangerous suspects.
A Foreign Office spokesman said he could not comment on individual cases.
"We regard the circumstances under which detainees continue to be held at Guantanamo Bay as unacceptable," he said.
"As the prime minister has said, Guantanamo should be closed.
"We are not in a position to provide consular or diplomatic assistance to foreign nationals in Guantanamo Bay.
"However we have, exceptionally, met the families and representatives of these men and have conveyed their concerns to the US on a humanitarian basis."
David Johnson, from the US embassy in London, said America was working to close the detention camp. But he refused to comment on any discussions with other nations about the detainees.
Clive Stafford Smith, a lawyer working for the release of detainees at Guantanamo, described UK fears about monitoring the men if they did return as a "red herring".
He told BBC Radio 4's World At One: "My clients say they don't care if the British government watches them on the toilet - they will come back here."
Liberal Democrat leader Sir Menzies Campbell said the government should not shirk its moral responsibility.
"What is the point of the attorney general and lord chancellor condemning Guantanamo as legally unacceptable when the British government, at the same time, is unwilling to take back UK residents who are detained there?
"The government really needs to make up its mind."