President Obama announced Thursday that U.S.-led airstrikes have broken the siege by Islamic militants against religious minorities who were trapped on a mountain in northern Iraq -- but made clear the U.S. mission in the region is not over yet.

The president, in brief remarks from Martha's Vineyard where his family is on vacation, said he expects the specific operation at Mount Sinjar to wind down. He said military planners will be leaving in the coming days, aid drops will stop and a U.S.-led evacuation is likely no longer needed.

"The situation on the mountain has greatly improved," Obama said. "We broke the ISIL siege of Mount Sinjar. We helped vulnerable people reach safety."

But Obama said U.S. involvement will not come to an end, as militants with the Islamic State -- also known as ISIS, or ISIL -- continue to brutalize the civilian population in the region, especially minorities like Iraqi Christians and Yazidis.

Obama said "we will continue airstrikes" where necessary to protect American personnel and facilities in Iraq.

And he said the U.S. is working with partners to provide humanitarian aid to "those who are suffering in northern Iraq wherever we have capabilities."

He reiterated that this would not commit "combat troops on the ground," but, while green-lighting additional airstrikes, said the U.S. also has increased military assistance to Iraqi and Kurdish forces.

In committing the U.S. to staying engaged in the region, the president acknowledged what U.S. lawmakers and other allies have been saying for weeks, if not months.

"The situation remains dire for Iraqis subject to ISIL's terror throughout the country," Obama said.

Pentagon spokesman Rear Adm. John Kirby said later Thursday that "our efforts there are not over," while noting the "limited military objectives" of the mission: protecting Americans, advising and assisting Iraqi forces, and addressing the humanitarian crisis.

"While our airstrikes and our humanitarian aid have had an impact on the situation in northern Iraq, there is still no American military solution to the larger crisis in Iraq," Kirby said. "The only lasting solution is for the Iraqis to come together and form an inclusive government that represents the legitimate interests of all Iraqi citizens."

Earlier Thursday, military officials said U.S. aircraft struck and destroyed two ISIS-armed vehicles and an ISIS-operated mine-resistant vehicle northeast of Irbil. All U.S. aircrafted completed the mission safely.

The developments come one week after Obama first authorized airstrikes and aid drops to help the thousands of Yazidi refugees trapped on the mountain, after being driven out by Islamic State militants.

Obama said U.S. forces delivered more than 114,000 meals and 35,000 gallons of water. Together with airstrikes and efforts by international partners and Kurdish security forces, Obama said thousands of people already have been able to evacuate. Those still there, he said, continue to leave.

Officials said there were about 4,500 Yazidis left on the mountain, and that half were herders who want to stay.

Though it's not clear whether they are out of danger, Obama said he does not expect the U.S. to launch an evacuation operation -- as had been discussed earlier this week -- or to continue humanitarian aid drops on the mountain.

Still, the administration's decision to pursue other humanitarian missions and keep a military presence signals lingering concerns about the deteriorating security situation in the country.

For months, administration officials had been divided about the threat posed by the Islamic State as it seized parts of Syria and advanced on towns in Iraq. Now, amid new intelligence about its growing strength, a consensus is forming that the group presents an unacceptable terrorism risk to the United States and its allies.

Defense Secretary Chuck Hagel said the group poses "a threat to the civilized world," while Senate Intelligence Committee Chairwoman Dianne Feinstein, D-Calif., called the Islamic State a "terrorist army" that must be defeated.

But Obama has not used similar language. He has authorized a limited campaign of targeted airstrikes designed to protect refugees and American personnel in the Kurdish region -- but not take out the group's leadership or logistical hubs.

He did not signal a broader mission in his remarks on Thursday afternoon.

A strategy to destroy the Islamic State would not necessarily require large numbers of American ground troops, but it would amount to a significant escalation from the recent air operations, analysts say. It might also require military action in western Syria, where the group has its headquarters in the city of Ar-Raqqah.

Proponents of doing so argue that the Islamic State must be stopped because it will destabilize America's allies in the region and eventually export terror to Europe and the U.S. Critics of the idea are urging the president just as strongly not to get sucked into another Middle East war, arguing that years of American micromanagement in that region have ended in tears.

Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said during a security forum in Aspen, Colorado, last month that the military is "preparing a strategy that has a series of options to present to our elected leaders on how we can initially contain, eventually disrupt, and finally defeat (the Islamic State group) over time."

Obama's GOP critics fear that the president will shy away from such a strategy because it repudiates what they say was his misguided decision to disengage from Iraq. Two years ago, the president resisted the calls of his advisers to aggressively arm moderate rebels in Syria.

"You can almost hear the angst in the voices of our military commanders connected to what they know is a fundamental mismatch" between the threat and the strategy, said Rep. Mike Pompeo, R-Kan., a former Army officer and member of the House Intelligence Committee. "President Obama absolutely is refusing to acknowledge the threat to America and respond in a way that is appropriate."

Ben Rhodes, White House deputy national security adviser, rejected that view. "We absolutely believe that (the Islamic State) poses a threat to U.S. persons and personnel," he said Wednesday. "We're focused on dealing with that threat right now in Iraq so that the terrorists cannot advance on Irbil," the Iraqi Kurdish capital.

The Associated Press contributed to this report.