British Prime Minister Tony Blair paid a surprise visit to Iraq on Thursday, saying the country's security and political situation had improved over the last year, but refused to set a timetable for the withdrawal of British troops. "You don't set an arbitrary timetable," Blair said, briefing reporters at a British logistics base near Basra in southern Iraq. "The whole purpose is to build up the Iraqi security forces so we can draw down our own strength." Their presence, almost three years after the March 2003 invasion, continues to depress Blair's popularity at home. Britain's military contingent in Iraq, based around Basra, is the second largest after that of the United States. Ninety-eight British troops have died in Iraq since the invasion. Blair has repeatedly said British troops will not leave Iraq until they are asked to go by the Iraqi government.