BAGHDAD — The Iraqi central government followed U.S. forces in delivering massive amounts of aid Saturday to refugees stranded high in the Sinjar mountains after they escaped a Sunni militant takeover of their towns, and President Barack Obama warned Americans that the renewed U.S. military campaign in Iraq will be “a long-term project.”

Iraq’s defense ministry released a video showing a fleet of C130 cargo planes, each carrying 20 tons of foodstuffs and water, dropping the aid to people in the mountains earlier Saturday. The video shows aerial views of hundreds of cars on top of the mountain and men rushing to collect the deliveries.

President Barack Obama wouldn’t say Saturday just how long the U.S. military involvement would last. He said it depends on the Iraqi government’s sincerity in bringing feuding political parties and sectarian groups together to combat the crisis.

“I don’t think we are going to solve this problem in weeks,” Obama said. He described the militant takeover of large parts of Iraq as “a wake-up call for a lot of Iraqis inside of Baghdad” who must cooperate to keep their country from breaking up.

The U.S. military, which officially withdrew its combat forces from Iraq in late 2011 after more than eight years of war, returned to battle Friday when two F/A-18 jets dropped 500-pound bombs on a piece of artillery and the truck towing it outside Irbil.

The Pentagon said the militants were using the artillery to shell Kurdish forces defending the capital of Iraq’s autonomous Kurdish region, home to a U.S. consulate and about three dozen U.S. military trainers.

A second round of airstrikes by four Navy F/A-18 fighter jets destroyed a seven-vehicle convoy, and unmanned aircraft hit a mortar launcher near Irbil, according to U.S. officials who spoke on condition of anonymity because they weren’t authorized to discuss the strikes publicly.

American planes dropped food and water on Friday and Saturday for those trapped in the Sinjar mountains, said Pentagon chief spokesman Rear Adm. John Kirby.

Iraq’s embattled Prime Minister Nouri al-Maliki called upon his air force on Monday to provide aerial reinforcements to Kurdish fighters on the front lines of battle against the Islamic State militants.