WASHINGTON - The United States is ramping up its military presence in Iraq, deploying around 300 additional troops as well as helicopters and drone aircraft in response security concerns in Baghdad, officials said on Monday.

Iraqi people walk past policemen keeping guard as part of an intensive security deployment on the al-Falahat bridge north of Baghdad June 30, 2014. Iraqi security forces intensified security measures in and around capital as Iraqi troops battled to dislodge an al Qaeda splinter group from the city of Tikrit after its leader was declared caliph of a new Islamic state in lands seized this month across a swathe of Iraq and Syria.  [Photo/Agencies]

The decision announced by the Pentagon puts US military personnel in a security role at Baghdad International Airport in the face of advances by an al Qaeda splinter group, three years after America's military withdrawal.

As speculation swirls about whether President Barack Obama might authorize US air strikes, a US defense official said the moves were primarily focused protection of American personnel in Iraq, including civilians.

"This is not about (preparations) toward air strikes," the official said, speaking on condition of anonymity.

The Pentagon said about 200 forces arrived on Sunday in Iraq to reinforce security at the US embassy, its support facilities and Baghdad International Airport.

Another 100 personnel arrived in Iraq and many would be stationed at the airport, the official said.

"I think there's an appropriate level of concern about the airport," the official said, noting it was a vital transportation hub.

The Pentagon said a small number of helicopters and drone aircraft were also being deployed to Iraq.

The forces are in addition up to 300 military advisors that Obama authorized to be deployed to Iraq partly to set up two joint operations centers. They also will assess how the United States might provide additional support. About 180 of those advisers are already in Iraq.

The troop movements are part of the Obama administration's attempt to help Iraqi Prime Minister Nuri al-Maliki's push back militants from the Islamic State in Syria and the Levant (ISIL), who have made stunning advances over the last few weeks.

Another US official, speaking on condition of anonymity, said the United States was also considering putting up a new joint military operations center in the northwest of Iraq's semi-autonomous Kurdish region.

While no final decisions have been made, the official said the new operations center, which would be the second the United States has established since Iraq's security deteriorated earlier this month, could be placed in the province of Duhok, in Iraq's farthest northern reaches near Syria and Turkey.

US forces at a similar joint operations center in Baghdad are gathering information about the situation on the ground and overseeing US forces who are taking stock of the Iraqi military in the field.

It was not immediately clear whether US forces at the new joint operations center would be working primarily with the Peshemerga, the Kurdish forces that have long protected Iraq's Kurdish enclave, or whether forces from the Iraqi military commanded from Baghdad would be involved.