British Prime Minister Tony Blair on Tuesday said that the war against Iraq is proceeding "exactly as we thought it would".

"Within five days of the conflict beginning, we are 100km south of Baghdad; a large part of Iraq has been secured and each of the main strategic objectives has been achieved," Blair said at his monthly news conference in London.

"The forces have achieved a huge amount in the war so far," he said and assured the Iraqis that coalition forces would not let them down.

"Saddam Hussein and his regime will be removed. Iraq will have a better future ahead of it," he said.

Blair said he would fly to meet US President George Bush on Wednesday, before holding talks with UN Secretary-General Kofi Annan the next day.

The prime minister admitted that there would be casualties in the war.

"War is always like that, but the strategy... is taking shape exactly as we thought it would."

 He refused to comment on US reports that Saddam had given the order for chemical weapons to be used in the defence of Baghdad.

"But from the outset the coalition has to be on its guard about the possibility of Saddam using chemical or biological weapons," he said.

Coalition forces are moving towards Baghdad in a two-pronged advance and lead elements of the US 5 Corps have now reached the town of Karbala, 80km south of the Iraqi capital, he said.