Defense Secretary Donald H. Rumsfeld said Wednesday on an unannounced visit to an air base north of Baghdad that the new Iraqi government was not yet ready to decide on security issues that will determine the pace of US troop reductions this year. Speaking to reporters on a flight from Afghanistan, Rumsfeld said the Iraqis are embarked "on a comprehensive review" of their security requirements, as well an effort to reconcile Sunni and Shiite groups to broaden political support for the government. Asked how long that might take, he said, "I don't talk deadlines." Rumsfeld was met at his airplane by Gen. George Casey, the top American commander in Iraq. The secretary was holding a town hall style meeting with troops at the air base and later meeting with Iraqi and US military and civilian officials.