The United States was deploying extra troops in Iraq and mulling air strikes against Takfiri militants who have been fighting the Iraqi government.

The United States was deploying extra troops in Iraq and mulling air strikes against Takfiri militants who have been fighting the Iraqi government.

President Barack Obama announced that about 275 military personnel were being deployed to Iraq to help protect the embassy in Baghdad and assist US nationals there.

The force, which began deploying on Sunday, has been sent "for the purpose of protecting US citizens and property, if necessary, and is equipped for combat," Obama said in a letter to Congressional leaders.

"This force will remain in Iraq until the security situation becomes such that it is no longer needed."

Washington has already deployed an aircraft carrier to the Gulf, but Obama has ruled out a return to Iraq for US soldiers, who left the country at the end of 2011 after a bloody and costly invasion launched in 2003.

The Takfiris are said to have killed scores of Iraqi soldiers as they pushed an advance on the capital, including in a horrifying massacre that has drawn international condemnation.

Meanwhile, US Secretary of State John Kerry said on Monday that drone strikes could be used, after Obama said he was considering "all options" on how to support the Iraqi government.

Drones might not be the "whole answer," Washington's top diplomat told Yahoo News, "but they may well be one of the options that are important to be able to stem the tide and stop the movement of people who are moving around in open convoys and trucks and terrorizing people".