The US Senate's Republican leader hailed the handover of Iraq's Muthanna province to local authorities as a "significant milestone" for the country.
"Muthanna will become the first province in which civilian Iraqis take charge of Iraqi security forces in that province," US Senator Bill Frist said.
"The handover of Muthanna is a critical step in the chain of events leading to Iraq standing entirely on its own. It marks a new phase in the history of Iraq."
"It means the increasingly capable Iraqi security forces and government are ready to operate independently -- and to replace coalition forces," Frist added. "And it means the president's strategy for Iraq is working."
Since 2003, the US military, along with Australian, British, and Japanese forces, have worked together to ensure the security of Muthanna, a relatively stable southern province of Iraq.
Coalition forces will remain in the province but will be pulled from urban areas and largely assume a supporting and advisory role.
The transfer means that the governor will maintain security with provincial police forces and can call for help from central government, which remains in command of army and national police forces located in the province.
"The Iraqi security forces are growing, as are their capabilities and responsibilities," said Frist.