BAGHDAD, Iraq (CNN) -- The U.S. military formally handed authority over Baghdad's "Green Zone" to Iraqis on Thursday as new pacts governing the mission of international troops replaced a U.N. mandate. An Iraqi honor guard parades outside the former palace of Saddam Hussein in Baghdad on Thursday. Iraqi troops took over checkpoints around the heavily protected district, formally known as the International Zone, which houses Iraqi government offices and the U.S. Embassy. Saddam Hussein's Republican Palace, which served as U.S. headquarters in Baghdad after the 2003 invasion that ousted Iraq's longtime strongman, was among the facilities handed over in Thursday's ceremony.
@highlight
U.N. mandate authorizing foreign troop presence expired Wednesday
@highlight
New bilateral pact covers U.S. presence until 2011
@highlight
U.S. troops to leave Iraqi cities by end of June
Perkins said American troops will continue to fight alongside @placeholder -- "but the Iraqis will be in the lead."