“The threat is real, it is acute, it is persistent and it is something that we are focused on with every tool in our arsenal,” Sullivan said on CNN’s “State of the Union” on Sunday. “We are working hard with our intelligence community to try to isolate and determine where an attack might come from.”

Terrorism has emerged as an acknowledged risk in recent days as some 6,000 U.S. troops seek to ensure what President Joe Biden has pledged to be an orderly and safe withdrawal from the Afghan capital. Islamic State has had a presence in Afghanistan for years, often striking against Taliban targets as well as Afghan government targets.

Biden is meeting with his national security team on Sunday morning and has scheduled a news conference on topics including Afghanistan for 4 p.m. in Washington. The president will hold a virtual meeting with other Group of Seven leaders on Tuesday to coordinate evacuations and discuss humanitarian aid for Afghan refugees, White House spokeswoman Jen Psaki said.

The Defense Department ordered U.S. airlines to provide 18 planes to transport evacuees, saying the extra capacity will help military aircraft focus on operations in and out of Kabul.

Activation of the Civil Reserve Air Fleet program involves four planes from United Airlines, three each from American Airlines, Atlas Air, Delta Air Lines and Omni Air and two from Hawaiian Airlines, Pentagon spokesman John Kirby said in a statement Sunday.

The activated aircraft won’t fly into the Kabul airport, where chaotic scenes of people desperate to leave the Afghan capital have been playing out. Instead, they’ll be used for onward movement of passengers from temporary safe havens and interim staging bases, Kirby said. No major impact on U.S. commercial flights is expected, he said.

The U.S. and its allies airlifted a combined 7,800 people out of Kabul in the latest 24-hour period, Sullivan said.

Some 25,000 people have been evacuated since Aug. 14, he said on NBC’s “Meet the Press.” While the U.S. has sufficient forces on the ground, Biden asks his commanders “every single day” whether they might need more resources, Sullivan said.

Thousands More

Several thousand U.S. citizens are still believed to be in Afghanistan, though it’s hard to determine a more exact number, Sullivan said.

In Kabul, U.S. commanders “have a wide variety of capabilities that they are using to defend the airfield against a potential terrorist attack,” he said. “We are taking it absolutely, deadly seriously.”

Biden has faced criticism from across the political spectrum and from some U.S. allies for his handling of the U.S. troop withdrawal from Afghanistan. He has set an Aug. 31 deadline, while suggesting that evacuations may continue beyond that date.

The president’s approval rating declined to 50% in a CBS News poll published Sunday, compared with 58% in July and 62% in March. While only 47% approved and 53% disapproved of his handling of the Afghan withdrawal, 63% backed removing U.S. troops from the country. The Aug. 18-20 poll of 2,142 adults has a margin of error of plus or minus 2.3 percentage points.

Republican critics called on Biden to abandon the Aug. 31 cutoff for withdrawing from Afghanistan and widen the U.S. military’s perimeter beyond Kabul airport.

“August 31 was a stupid, arbitrary, politically driven deadline,” Senator Ben Sasse, a Nebraska Republican, said on “Fox News Sunday.” “The Taliban needs to know, they don’t dictate the timetable on American lives.”

Representative Adam Kinzinger, an Illinois Republican who served in the Air Force during the U.S. military campaigns in Iraq and Afghanistan, said “we’re in a better place than we were a week ago.”

“That doesn’t mean we’re in a good spot,” he said on CNN. “This was a disastrous withdrawal from Afghanistan.”

Citing Sullivan’s comments on the ISIS threat, Kinzinger said: “So how is it that we leave Afghanistan?”

The Biden administration has said that the threat from al-Qaeda, which carried out the Sept. 11, 2001 attacks on the U.S., has been eliminated to the point of allowing a withdrawal from Afghanistan and that terrorist threats can be intercepted with “over the horizon” capabilities.

–With assistance from Ian Fisher and Eric Martin.