British Foreign Secretary Jack Straw said on Monday British troops in Iraq were likely to stay there for years, maybe until 2006 or 2007.
Speaking on BBC radio a day after Prime Minister Tony Blair paid a surprise visit to British soldiers in southern Iraqi city of Basra, Straw said it was "a fact" that substantial number of troops would remain in Iraq for a long time to come.
"I can't give you an exact time-scale ... but it's not going to be months, for sure," Straw said.
Asked whether it would be years, he replied: "Yes, but I can't say whether it's going to be 2006 or 2007."
Blair, Washington's chief ally in invading Iraq last March and occupying it since, visited Basra on Sunday and told British troops they were "new pioneers of soldiering," fighting against terrorism, weapons of mass destruction and brutal regimes.
Some 45,000 British troops were part of the original US-led invasion force - the largest British deployment since the Korean war 50 years ago - but numbers have been steadily reduced. Around 10,000 Britons are now serving in the country.
Blair urged soldiers to concentrate on winning the peace in a country riven by a relentless insurgency against occupying forces, saying that would ensure a stable future. He said the effort would take time and indicated the troops would be there for the long haul.
Straw said British troops were key to providing the stability in Iraq that was needed to allow a political process to proceed.
"If we were suddenly to pull out, there would unquestionably be a security vacuum," he said. "And that would not only put lives at risk ... but it would also be a setback for the political process."
US administrators in Iraq have set a timetable to hand over power to Iraqis by the end of June.
Blair used his speech to the troops on Sunday to reiterate his firm belief that he and US President George W. Bush did the right thing in invading Iraq.
Blair made weapons of mass destruction the main justification for joining the US-led invasion in the face of stiff domestic opposition. No such weapons have yet been found.