The US is not being unreasonable in its approach to the release of British detainees at Guantanamo Bay, the prime minister has said.

Tony Blair said on Tuesday that were the four remaining Britons released he was not yet satisfied that the necessary arrangements are in place to ensure the protection of the UK's security.

He told the Commons liaison committee that the government would need to be "very, very clear" that there was a system in place to protect national safety.

"I do not think the United States is being unreasonable in saying that we need to make sure there is proper security in place for these people," Blair said.

"What is going on is an attempt to make sure we can meet our own security requirements.

"I just have to be careful in terms of the security of this country."

Emphasising the point, the prime minister added: "I need to be very clear in respect of our own country that we are not putting anyone at risk."

"I am not yet satisfied that we have the necessary machinery in place, but we are working on that," he said.

While not explaining the detail of individual cases, Blair said their detention "did not arise out of some random event".

The comments came as lawyers for the detainees continue to press for their clients' release.

Following a US supreme court ruling last week, the detainees now have access to the American court system.

Blair also went on to defend his close relationship with the US.

"I believe it is in our interests to have this strong relationship with the United States of America," he said.

"It is a shame that here it is seen somehow as a sign of mockery that we have the closeness of that relationship."