President Barack Obama has said that the United States will not be sending its troops back to Iraq, but is reviewing other options to assist the Iraqi government threatened by an advancing armed group.

"We will not be sending US troops back into combat in Iraq, but I have asked my national security team to prepare a range of other options that could help support Iraqi security forces," Obama said on Friday.

"The US will do our part, but ultimately it's up to the Iraqis, as a sovereign nation, to solve their problems," he said, speaking at the White House lawn.

He said that the Islamic State of Iraq and the Levant (ISIL) has made significant gains in Iraq and that the armed group had overrun part of the country.

The threat by ISIL fighters in Iraq poses a danger to the people of Iraq and also, potentially Americans, Obama said.

Military aid

Administration officials said Obama was considering air strikes using drones or manned aircraft. Other short-term options include an increase in surveillance and intelligence gathering, including satellite coverage and other monitoring efforts.

The US also is likely to increase various forms of aid to Iraq, including money, military training and both lethal and non-lethal equipment.

Obama added that Iraq's government must make a sincere effort to address sectarian differences, or else US military help would not succeed in curbing the violence there.

He suggested it could take several days before the administration finalises its response to the situation on the ground.

The last US troops withdrew from Iraq in 2011 after more than eight years of war.