The No. 2 US commander in Iraq said the next three to four months will be crucial in determining whether the United States can start to withdraw troops from Iraq without sacrificing security gains since the troop buildup began early this year. Lt. Gen. Raymond Odierno said Tuesday the number of attacks in August fell to their lowest level in more than a year, although he gave no figures. Odierno insisted that overall violence was declining - a sign that the buildup ordered by US President George W. Bush was working. "I think the next three to four months are critical," Odierno told reporters. "I think that if we can continue to do what we are doing, we'll get to such a level where we think we can do it with less troops." Bush himself raised the possibility of a reduction in the 160,000-strong US force during his surprise visit Monday to al-Asad Air Base in Anbar province, where Sunni Arab sheiks have been turning against al-Qaida in Iraq.