The British situation in Iraq is "different in many critical respects" to that of the US, Tony Blair has insisted as George Bush prepares to announce further deployment of troops.
The US president is expected to say that 20,000 more US soldiers will be sent to Iraq, despite calls from both sides of the Atlantic for coalition forces to begin withdrawing from the increasingly violent country.
Liberal Democrat leader Menzies Campbell pressed Mr Blair on whether he would be following President Bush's lead, to which he replied that the situation in Baghdad - where the Americans are based - was very different from that in British-controlled Basra.
However, the prime minister defended his close relationship with the White House, saying it was an "important part of our foreign policy" and it was the duty of the government to keep both this and Britain's ties with the European Union "strong".
"President Bush will set out the policy for US forces particularly in respect of Baghdad later today. Let me just make one thing very clear, however - in relation to Basra, the situation is different in many critical respects," Mr Blair said during prime minister's questions.
"First of all in respect of Basra we do not have the same Sunni-Shia violence, we do not have al-Qaida operating in same way, and we do not have Sunni insurgents operating in same way."
He said recent operations in Basra to help hand over control of policing and security to the Iraqi authorities had been successful, and the aim of the US forces in Baghdad was similar, but as a result of the different circumstances, less advanced.
However, Sir Menzies continued to demand that the prime minister distance himself from American policy, noting that Gordon Brown indicated this weekend that he would pursue such a stance if, as expected, he takes over from Mr Blair this summer.
"At the weekend, the chancellor of the exchequer made it clear that he favours an independent foreign policy - do we now have to wait for resignation of the prime minister to get one?" the Lib Dem leader asked.
Mr Blair responded: "The alliance of Britain with the United States of America, in my view, is in the British national interest, I think it is an important part of our foreign policy.
"I think there are two great relationships that Britain has in the world - one with America, the other with Europe - and we should maintain both and keep them strong."
Mr Blair said he would report back to the House of Commons on the situation in Iraq once the current operation in Basra was complete.