The Pentagon said Monday that commercial power has still not been restored to the Incirlik Air Base in southern Turkey, where about 2,700 U.S. defense personnel are based, along with a number of U.S. nuclear warheads.

"Power has not yet been restored, but our operations there do continue," Pentagon press secretary Peter Cook told reporters at a briefing.

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He said U.S. forces at the base continue to rely on back-up power generators, as has been the case since commercial power was cut off in the wake of an attempted military coup in Turkey on Friday.

Cook said all U.S. defense personnel, their families, and military facilities inside Turkey -- presumably the ones containing about 50 nuclear weapons -- were secure.

"I will just say, broadly, that we've taken appropriate steps to maintain the safety and security of our personnel, our civilian and military personnel, their families and our facilities. And we will continue to do so," Cook said.

The Pentagon has an additional 1,000 personnel based at other locations in Turkey, and about 100 dependents. All other dependents were asked to leave the country last year amid worsening security conditions in the country.

Cook said U.S. air operations launched from the base against the Islamic State in Iraq and Syria (ISIS) continue, but they could be impacted if power is not restored after a "protracted" period.

At that point, the U.S. would have to make the appropriate adjustments, such as flying aircraft from other bases in the region to continue operations against ISIS, Cook said.

"I think it's safe to say over time that it could become a limiting factor," he said. "The concern would be if it were a protracted period of time, then we would potentially have to make adjustments."

The U.S. has KC-135 refueling aircraft, as well as A-10 attack jets and drones based at the air base, about 110 kilometers from the northern Syria border. The U.S. last year clinched a much-touted agreement with Turkey to use the air base in its operations against ISIS, since it is closer to the fight than other U.S. air bases in the region.

"Incirlik is obviously an important part of our military campaign ... and it will continue to be an important part of the campaign," Cook said.

Cook said Defense Secretary Ash Carter has not yet spoken with the Turkish defense minister, but looked forward to doing so "in the near future."

He also said the Pentagon was caught off guard by the coup, as were other U.S. government agencies.

"I think it's fair to say that the — that the secretary was surprised by — by the activities on Friday, as others in the U.S. government were," he said.

"I think it was not just the Department of Defense, but others who were surprised by the events that played out on Friday. And there will be, I'm sure, an effort to assess if there was — should have been more information that we should have obtained previously," he said.

Cook said there was nothing to indicate that cooperation with Turkey against ISIS would be impacted.

"We don't see any reason why that can't continue," he said.

-- Updated 11:36 p.m. ET