Significant numbers of British soldiers could leave Iraq within 18 months, Prime Minister Blair said yesterday.

He also promised that troops in Afghanistan would get any additional forces and equipment they needed.

Mr. Blair said he had not yet received a request for more manpower for Afghanistan, but assured a parliamentary committee that any such request would receive a positive response.

“Anything they need and ask for in order to protect our troops, I will make sure they get. Our obligation to them is to give them what they need to do the job,” he said.

He denied that the mission in Helmand province had become “confused” over the various aims of combating the Taliban, supporting reconstruction, and tackling the opium trade.

But, after the death of five soldiers, he acknowledged that the mission was dangerous and “going to be a lot more dangerous.”

Mr. Blair said the work being carried out by British troops was “absolutely vital” for the future of the country.

“If the Taliban get a foothold back in Afghanistan, then the very reasons why we had to go into Afghanistan will all reappear with all the consequences for our own security and the security of the wider world,” he said.

Mr. Blair was questioned by Labor and Conservative MPs over the worsening security situation in Iraq – including the southern city of Basra in the British-controlled sector – and the prospects for the eventual withdrawal of British troops.

He refused to set a time scale for the total withdrawal of forces, saying they would remain in Iraq as long as the government there wished them to.

But over the next 18 months there would be opportunities to draw down significant numbers because the capacity of the Iraqi troops would build up.

The Labor chairman of the foreign affairs select committee, Mike Gapes, told Mr. Blair he made several visits to Basra, and each time security had deteriorated.

Mr. Blair said the presence of British troops was used by some extremist groups as an excuse for violence. But he said the elected representatives of the democratic government in Iraq did not want British troops to leave at this stage.

He was involved in sharp exchanges with the Tory chairman of the public accounts committee, Edward Leigh, who said thousands of Iraqis have died since the invasion and life for ordinary Iraqis was worse than under Saddam Hussein.

Mr. Leigh said he had been able to walk the streets of Baghdad in Saddam’s time, but nobody in the room would walk in Baghdad now.