US Defense Secretary Robert Gates was cautious in his assessment of progress in the Iraq war as he prepared to meet Saturday with top U.S. military and civilian officials and the Iraqi prime minister. Gates made his fourth trip to Iraq to assess progress now that the buildup of troops ordered by US President George W. Bush has been completed. Gates landed Friday in a city locked down due to a recent mosque bombing. He is the third top US official to travel to Baghdad this week to press the Iraqi government to move more quickly toward political reconciliation and other vital reforms that many see as critical to gaining control of violence in the country. The top US commander in the Middle East, Adm. William Fallon carried that message to the Iraqis last weekend, and John Negroponte, the No. 2 State Department official, reinforced it in a visit midweek. En route to the war zone, Gates said it "remains to be seen where we'll be in September" when he is to make a formal assessment of whether the Iraqi government is making the kind of progress demanded by the Bush administration and an increasingly impatient Congress. His cautious tone reflected a growing sentiment among military leaders that they may not be ready to make a full review of the effects of the US troop buildup that Bush ordered earlier this year to try and stabilize Iraq.