Tony Blair will mount a strong defence of his actions over Iraq when he travels to Washington for talks with President George Bush later this week.
The Prime Minister will appeal to his critics to look at his record in a different light after the formation of an Iraqi government. He will say the war in Iraq was in line with an interventionist or "activist approach" to foreign policy he also pursued in Kosovo and Sierra Leone, which enjoyed greater public support.
He will also say it was consistent with his policies on the Middle East, Africa and climate change.
Mr Blair will say he floated the idea of humanitarian interventionism, dubbed "liberal imperialism" by some of his advisers, in a speech in Chicago in 1999.
In the last of three speeches on foreign policy, Mr Blair will call for reform of the United Nations, saying that today's international institutions were designed for the Cold War era.
He believes that the UN's failure to approve a fresh resolution authorising military action in Iraq in 2003 showed that the organisation shies away from rather than confronts problems.
The Prime Minister believes that the formation of the Iraqi government provides an opportunity for him to answer critics who believe the war had little to do with promoting the democratic values he espouses.
Although he hopes the new government in Baghdad marks a turning point in Iraq's fortunes, aides accepted yesterday that a long haul still lies ahead as the country remains racked by sectarian conflict and terrorism. "It is difficult, it will continue to be difficult," one government source said.
President Bush and Mr Blair will discuss a timetable for withdrawing US and British troops from Iraq but are likely to be cautious in their public statements about it. They will pledge to stay until they have "finished the job".
The two leaders, who have seen their opinion poll ratings slump as they serve their final terms, will also discuss Russia, the Middle East and Iran's nuclear plans.
Margaret Beckett, the Foreign Secretary, played down the prospects for an early withdrawal of British troops from Iraq. She said there was no question of "cutting and running" and the troops would remain as long as they were needed to assist the Iraqi government.
She told the BBC's Sunday AM programme that the handover to Iraqi forces would be considered on a "case-by-case" basis as the security situation in cities and provinces was considered. "It is dangerous in this kind of situation to set artificial deadlines," she said. "Things will go forward as it seems sensible and safe to do so. We have said for a long time that the British troops will stay there - and the coalition troops will stay there - while there is a job that needs to be done."
Lord Owen, a former Labour foreign secretary, attacked the "sheer damned incompetence" of the US/UK mission in Iraq and accused Mr Blair of trying to act as his own foreign secretary and defence secretary by moving the people who held those posts in the Cabinet reshuffle.
He told GMTV's Sunday programme: "That's what landed us in the mess we're in in Iraq and it's an utter folly to believe that a Prime Minister can handle the day-to-day issues which are so complex in Iraq and Iran."Reuse content