Tony Blair has implied no more UK troops will be sent to Iraq, despite a commitment from the US to send another 20,000 soldiers to Baghdad.
Mr Blair says policy in Iraq remains the same
Asked if more troops would be sent, the prime minister told MPs UK troops did not face the difficulties in Basra that US troops encounter in Iraq's capital.
He said the operation to allow Iraqi forces to take over Basra's security should end "in the next few weeks".
President Bush said the US planned to send 20,000 more troops to Iraq.
Mr Blair was asked at his weekly question time session how many British troops he expected to commit, ahead of President Bush's announcement.
He told MPs: "In relation to Basra the situation is different in some very critical respects.
"We do not have the same Sunni-Shia sectarian violence, we do not have al-Qaeda operating in the same way and we do not have the Sunni insurgency operating in the same way."
"There has been an operation that the British have been conducting over the past few months that will be completed in the next few weeks.
"That operation, I'm pleased to say, has been successful, up to now. That will allow the Iraqis to take over more and more control of their own policing and security in Basra."
He said the aim of the US announcement would be the same - to allow the Iraqis to take over security progressively.
But Lib Dem leader Sir Menzies Campbell said: "The assumption behind that answer is that there will be no displacement of terrorist activity from Baghdad to Basra, which is an assumption that is very difficult to make at this stage."
He asked when Britain could expect an independent foreign policy - Mr Blair replied by defending the "important" alliance with the US.
Mr Blair was also asked if 2007 would see a "new and improved policy" in Iraq. He told MPs the policy remained the same, but once the operation in Basra was completed he would be happy to report back to the House of Commons.
President Bush said he would send more than 20,000 extra troops to Iraq, as part of a new strategy for tackling the conflict.
Sir Menzies has called the issue "a real test for the prime minister" and said Mr Blair must "assert the independence of British policy towards Iraq."