IRBIL, Iraq: US President Barack Obama has vowed to help rescue thousands of civilians besieged by militants on an Iraqi mountain, as Yazidi MP Vian Dakhil warned they would not survive much longer.

Obama gave no timetable for the first US operation in Iraq since the last American troops withdrew three years ago and put the onus on Iraqi politicians to form an inclusive government and turn the tide on militant expansion.

“The US can’t just look away. That’s not who we are. We’re Americans. We act. We lead. And that’s what we’re going to do on that mountain,” Obama said.

Obama has earlier said he will not allow militants to carve out a “caliphate” straddling Syria and Iraq.

US and Iraqi aircraft have air dropped food and water to the thousands of people, many of them members of the Yazidi minority, who have been stranded on Mount Sinjar since they fled Islamic State attacks on their homes a week ago.

Obama said he had received “strong support” from British Prime Minister David Cameron and French President Francois Hollande, who had both agreed to provide humanitarian assistance.