David Jackson

USA TODAY

President Obama said Saturday that airstrikes in Iraq will continue for as long as necessary to protect both U.S. personnel and religious minorities who are trapped on a mountain by militants in northern Iraq.

"I'm not going to give a particular timetable," Obama said at the White House shortly before leaving for a summer vacation at Martha's Vineyard, Mass. "We are going to maintain vigilance."

Obama again called on Iraq to form a unified government that is able to battle militants on its own, saying that "all Iraqi communities are ultimately threatened by these barbaric terrorists."

Overall, he said, improving Iraq's security situation will "take some time" and is "going to be a long-term project."

The president said that he and his aides will continue pushing Iraqi lawmakers to form a new government because they are the ones who must solve their nation's problems — "the United States can't do it for them."

Responding to a reporter's question, Obama said the U.S. did not leave troops in Iraq after the end of combat operations because Iraq's government did not sign an agreement to have them there.

Most of Iraq's citizens "did not want U.S. troops there," he said, adding that it's "bogus" for critics to attack him for the lack of a post-combat agreement.

The president said he has no plans to ask Congress for additional funds to finance the new operations in Iraq, but "we'll have to evaluate what happens over time."

The president also talked about Iraq during his weekly radio address, stressing the limited nature of renewed military action in Iraq and saying it is designed strictly to protect U.S. personnel and prevent a possible genocide of religious minorities.

"As commander in chief, I will not allow the United States to be dragged into fighting another war in Iraq," Obama told listeners.

The president said that "combat troops will not be returning to fight in Iraq, because there's no American military solution to the larger crisis there."

The radio address came two days after Obama authorized airstrikes against the militant group known as ISIS that is threatening the city of Irbil, where U.S. personnel are assisting Iraqi security forces.

U.S. airstrikes began Friday and continued Saturday.

The president also ordered air drops of food and water to religious minorities who are trapped on a mountaintop and under siege by the militants. In his radio address, Obama noted that he has approved "targeted American airstrikes to help Iraqi forces break the siege and rescue these families."

Obama said there have been two successful air drops in recent days.

The United States can't intervene in every crisis in the world, Obama said, but "when countless innocent people are facing a massacre — and when we have the ability to help prevent it — the United States can't just look away."

In addition to protecting U.S. personnel, Obama said that "we'll help prevent these terrorists from having a permanent safe haven from which to attack America. And we'll continue to urge Iraqi communities to reconcile, come together and fight back against these terrorists."

Congressional lawmakers expressed support for the new U.S. operations, though some Democrats want more specifics from Obama about an end strategy.

"I oppose open-ended military commitments, which the president's actions in Iraq could become," said Sen. Richard Blumenthal, D-Conn.

While supporting the humanitarian mission, Blumenthal said Obama "owes the American people a better, fuller explanation of the scope and strategy of military actions."

Some Republicans, meanwhile, said Obama should have a broader strategy for confronting the militants who have taken large swaths of land in Iraq and Syria.

Sen. James Inhofe, R-Okla., the ranking member of the Senate Armed Services Committee, described the strikes on the militants as long overdue.

"While the White House has been paralyzed by hand-wringing and indecision, ISIS now operates the largest terrorist safe haven in the world," Inhofe said.

The president and first lady Michelle Obama had planned a two-week vacation in Martha's Vineyard, though Obama will return to the White House for meetings on Aug. 17-19.