The marines and special operations forces will assess the humanitarian situation and will not be engaged in combat, a US defense official said.

The US has been carrying out airstrikes against ISIL Takfiri militants.

ISIL terrorists have forced tens of thousands to flee their homes.

"This is not a combat boots on the ground kind of operation," Hagel said, in remarks made at Camp Pendleton in California.

The "assessment team members" had arrived in the northern city of Erbil and would "give more in-depth assessment of where we can continue to help," he said.

The personnel are in addition to about 250 military advisers already in Iraq.

A US defense official said the government would continue to explore ways to support "Iraqis affected by the ongoing fighting in Sinjar", and to prevent "potential acts of genocide" by ISIL.

The UN has said that tens of thousands of civilians, including members of the Yazidi sect, are trapped on Sinjar mountain by ISIL fighters and need "life-saving assistance".

The UN says there are now an estimated 1.2 million internally displaced Iraqis.

The US has also reportedly begun supplying weapons to the Kurdish forces, known as Peshmergas, who have been fighting ISIL terrorists in the north.

The rapid advance across Iraq by ISIL militants has thrown the country into chaos.

ISIL overran Iraq's second largest city, Mosul, in June. They had taken the central city of Fallujah and parts of nearby Ramadi in December 2013.

BA/BA