WASHINGTON >> President Barack Obama on Saturday refused to give a time limit on America’s renewed military involvement in Iraq, saying he doesn’t think "we are going to solve this problem in weeks" as the country struggles to form a new government.

"I think this is going to take some time," he said at the White House before departing for a vacation on Martha’s Vineyard off the Massachusetts coast.

Obama warned Americans that the new campaign to bring security in Iraq requires military and political changes and "is going to be a long-term project."

The president said Iraqi security forces need to revamp to effectively mount an offensive, which requires a government in Baghdad that the Iraqi military and people have confidence in. Obama said Iraq needs a prime minister — an indication that suggests he’s written off the legitimacy of the incumbent, Nouri al-Maliki.

Obama said he won’t close the U.S. Embassy in Baghdad or the consulate in Irbil, which means American troops and diplomats will remain on the ground. He said he is obligated as commander in chief to protect U.S. personnel wherever and whenever they are threatened.

The president said humanitarian efforts continue to airdrop food and water to persecuted religious minorities stranded on a mountaintop, and he said planning was underway for how to get them down.

Obama made his comments and took a few questions from reporters on the South Lawn of the White House just before boarding Marine One for his summer vacation on Martha’s Vineyard in Massachusetts.

"I’m ready to not have a suit on for a while," Obama told reporters as he headed back into the White House before boarding the helicopter.

The president repeated that the U.S. will not have U.S. combat troops in Iraq again. "We are going to maintain that because we should have learned a lesson from our long and immensely costly incursion into Iraq," Obama said.

He dismissed the suggestion that the new military action in Iraq might cause him to regret pulling out troops in the first place. He said the departure of U.S. troops was the Iraqi government’s call because it failed to agree to legal immunity for American forces, which was the condition for them to stay.

Obama said that even if U.S. troops had remained, their presence would not have made much of a difference if the Iraqi government had followed the same political course of failing to incorporate the Sunni minority.

"The only difference is we would have a bunch of troops on the ground that would be vulnerable," Obama said.

"So that entire analysis is bogus and is wrong, but gets frequently peddled around here by folks who oftentimes are trying to defend previous policies that they themselves made," Obama said.

But in as much as Iraqi leaders couldn’t agree on immunity for U.S. forces, Obama also badly wanted U.S. troops out of Iraq to fulfill a campaign pledge.

The president said there’s "no doubt" the Islamic State’s advance on Irbil "has been more rapid than the intelligence estimates." But he said the airstrikes have destroyed the militants’ arms and equipment.

U.S. military jets launched several airstrikes Friday on isolated targets, including two mortar positions and a vehicle convoy. U.S. officials announced Friday night the second airdrop of food and water in as many days for the imperiled refugees.

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Associated Press writers Julie Pace and Erica Werner, and Nedra Pickler in Edgartown, Massachusetts, contributed to this report.