Tony Blair has said he was taken aback by the scale of the insurgency in Iraq.

The prime minister was facing a detailed grilling from senior MPs on a range of policy areas at his twice-yearly session in front of the Commons liaison committee.

Pressed on the progress of the war against terrorism he said the post-war uprising had been "astonishing in its wickedness".

But he insisted the recent elections had been a watershed for the country, despite the non-participation of the key Sunni community.

Blair denied the coalition had failed to plan properly for the post-conflict occupation and handover to the interim Iraqi administration

"The degree of the insurgency, in particular those people who come from outside Iraq, that was something that was difficult to foresee and difficult to plan for," he said.

"On the other hand it is was going to be difficult anyway. These people are obviously well armed and prepared to kill any number of people.

"The thing that has been most difficult has been this terrorism/insurgency."

He added that "that is something you can foresee and try to plan against".

"[But] the only thing you can do is to get after them as quickly as possible."

Troops

The prime minister again made clear that UK troops would remain in Iraq for as long as required by the new government.

"It is our desire that we go from Iraq as soon as possible," he told the committee. "The question is what is as soon as possible. It is when we have got the job done."

He argued that "the most effective way altogether is to build up the Iraqi capability".

"We are doing that and we are starting pretty much from scratch.

"To be fair, in the elections the Iraqi forces acquitted themselves pretty well. But they still need the multi-national force there."

Blair said he would consider publishing retired US General Gary Luck's review of the Iraqi security situation and future troop needs when it is finished.

"Over the next few weeks as the picture emerges more clearly and we get a new Iraqi government come into being, I hope we can then set out for people exactly what we then think is the way forward for the Iraqi-isation of security and outreach to some of the Sunni areas," he told the committee.

He said he hoped nations which had not taken part in the war against Iraq would agree at the forthcoming NATO meeting to help with security training.

"I think you may find, at the NATO meeting at the end of February, we get agreement on help for training Iraqi security forces," he said.

"I hope that will see some of the countries that haven't been involved either in the conflict or its aftermath involved in that."

And he claimed that some of the countries which have withdrawn their forces had "not changed their minds" on the war.

Iran

With Iran moving up the political agenda in Washington, Conservative MP Edward Leigh asked Blair whether "anyone would believe" him if he asked parliament to sanction strikes against the country because he claimed it had weapons of mass destruction.

The prime minister replied that he was "not saying that" and that he hoped the diplomatic strategy being pursued by Britain, France and Germany would persuade Tehran not to develop nuclear bombs.

"Secondly I think it depends what the evidence base is," he added.

However he conceded that "no one is disputing" that Iran has developed nuclear technology. "That is why France and Germany is working on this with us," he argued.

Blair warned that it would be wrong for Iran or Syria to assume that it was now "in their interests" to allow insurgents to cross into Iraq in order to weaken the Americans and reduce the chance of an attack on themselves.

"I think if they were to make that calculation it would be a very severe miscalculation," he said.

He also defended British intelligence in Iraq, despite acknowledged flaws.

"The Iraq Survey Group found that Iraq was indeed in breach of UN sanctions," Blair said.

Committee sessions

The sessions were introduced following the 2001 election in a bid to make the prime minister more accountable to parliament, beyond his weekly question time in the Commons.

Today's meeting is likely to be the last before the next Westminster poll, with the election expected to be called for May 5.

Blair is widely viewed as having performed strongly in the gruelling two hour appearances, with his grasp of detail and ability to focus on a range of issues often on show.