That raises the total U.S. troop presence in Iraq to approximately 750, the Pentagon said.
The State Department, meanwhile, announced that it was temporarily moving an unspecified "small number" of embassy staff in Baghdad to U.S. consulates in the northern city of Irbil and the southern city of Basra. This is in addition to some embassy staff moved out of Baghdad earlier this month,
Department spokeswoman Jen Psaki said the Baghdad embassy "will be fully equipped to carry out" its mission.
The White House announced that President Barack Obama had directed that 200 troops be sent to reinforce security at the embassy, its support facilities and Baghdad International Airport.
The Pentagon said the 200 arrived Sunday and Monday.
"The presence of these additional forces will help enable the embassy to continue its critical diplomatic mission and work with Iraq on challenges they are facing as they confront Islamic State in Iraq and the Levant," the Pentagon's press secretary, Navy Rear Adm. John Kirby, said in a written statement.
Obama notified House and Senate leaders in a letter on Monday of the additional forces heading to Iraq. Officials said they bring a detachment of helicopters and drone aircraft to improve airfield and travel route security in Baghdad.
Obama has ruled out sending combat troops back into Iraq. He said the extra troops will stay in Iraq until security improves so that the reinforcements are no longer needed.
Kirby said another 100 troops, who had been on standby in the Middle East since mid-June, also will move into Baghdad to provide security and logistics support.
That raises to about 470 the number of U.S. troops providing security in Baghdad.
Those forces are separate from the teams of up to 300 U.S. military advisers that Obama authorized for deployment to Iraq earlier in June. Of those 300, about 180 had arrived as of Monday, the Pentagon said. They are assessing the state of Iraqi security forces and coordinating with Iraqi authorities.
The U.S. also has a permanent group of about 100 military personnel in the Office of Security Cooperation, at the U.S. Embassy, to coordinate U.S. military sales.
AP National Security Writer Robert Burns contributed to this report.
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