Tom Vanden Brook and David Jackson

USA TODAY

WASHINGTON — President Obama vowed again Friday to help Iraq's government fight insurgents who are closing in on Baghdad, while a senior defense official told USA TODAY that American air power options are currently limited.

"The United States will do our part, but understand that ultimately, it's up to the Iraqis, as a sovereign nation, to solve their problems," Obama told reporters at the White House.

Obama also said: "We will not be sending U.S. troops back into combat in Iraq."

A senior defense official said U.S. air power options in Iraq are limited because the closest aircraft that could wage a bombing campaign against Islamist militants who have captured several of the nation's largest cities are at least 800 miles away.

The insurgents — the Islamic State of Iraq and Levant (ISIL), an al-Qaeda splinter group — started their offensive Monday. They are trying to create an Islamic territory including Iraq and Syria. They have taken Mosul, Iraq's second-largest city, and Tikrit, the birthplace of former Iraqi dictator Saddam Hussein.

To be effective, airstrikes would require the Iraqi army to step forward and engage insurgent forces on the ground, said the official, who spoke on the condition of anonymity because the details of potential air power options are not authorized to be released publicly.

In any event, U.S. warplanes are not based close enough at the moment to conduct such a campaign, he said.

"We have basically left Iraq," the official said.

Airstrikes in Iraq without an objective would be meaningless, the official said. If the objective is to roll back the gains of ISIL, then a determined ground offensive is required. Warplanes could help accomplish that objective but not complete it.

Obama, who was on his way to appearances in North Dakota and California over the next two days, said the planning for any type of American action "is going to take several days," and "people should not anticipate that this is something that is going to happen overnight."

The insurgents are about 100 miles from the Iraqi capital of Baghdad. The Iraqi military under Prime Minister Nouri al-Maliki has so far been unable to stop them.

At the White House, Obama said Iraq's government has been unable to deal with the "terrorist offensive," and he has conferred with his national security team about possible short-term military action.

The ISIL "poses a danger to Iraq and its people, and, given the nature of these terrorists, it could pose a threat eventually to American interests as well," Obama said.

So far, there do not appear to be any disruptions to Iraq's oil supplies, he said.

Obama also said that Iraq's government needs to deal with the sectarian divisions that have given risen to the violence. The problems with the morale and commitment of the Iraqi security forces are ultimately "rooted in the political problems that have plagued the country for a very long time."

The president also noted signs that the civil war in Syria has spilled over into neighboring Iraq.

"This is a regional problem, and it is going to be a long-term problem," he said.

Despite the limitations, Secretary of State John Kerry said Friday that Obama will act quickly.

"Given the gravity of the situation, I would anticipate timely decisions from the president regarding the challenge ... I am confident the U.S. will move rapidly and effectively to join with our allies in dealing with this challenge," Kerry said in London.

White House officials said they are assessing their options, both militarily and legally.

Obama "is considering all options in response to the question about potential direct action by the United States military," said White House spokesman Jay Carney. "But we would have to get back to you on how that would proceed if that decision were made."