The United States is increasing its military presence inside Iraq after President Obama said he would deploy around 300 additional troops and a detachment of helicopters and surveillance drones.
It brings the total number of US military personnel in Iraq to 750.
Pentagon spokesman Rear Admiral John Kirby said about 200 forces arrived in on Sunday to reinforce security at the US embassy and Baghdad International Airport. Another 100 personnel were also due to move to Baghdad to "provide security and logistics support."
The announcement comes after the 300 so-called “military advisers” that were green-lighted last week. The President had gone to lengths to suggest that they would not be engaged in combat but be training and assisting Iraqi forces fighting Isis militants.
But Mr Obama’s letter to the House of Representatives on Monday appeared to strike a different tone. "This force is deploying for the purpose of protecting US citizens and property, if necessary, and is equipped for combat," it said. "This force will remain in Iraq until the security situation becomes such that it is no longer needed."
There are now about 750 American military personnel in Iraq, including those stationed in the region since the official US withdrawal in 2011.
The new troop movement is part of the Obama administration's attempt to help Iraqi Prime Minister Nuri al-Maliki's repel the gains that militants from the Islamic State in Syria and the Levant (ISIL) have made over the last few weeks.