FIRST ON FOX: A former top Trump administration counterterrorism official said the Biden White House made a few critical missteps during evacuation efforts leading up to the deadly bombings near the Kabul airport Thursday that killed four U.S. Marines

Nathan Sales, the former ambassador-at-large for counterterrorism under former President Trump, told Fox News in an exclusive interview that Biden's "most important misstep" was the decision to leave the Bagram Air Base, which is more remote and in a better location to aid evacuation efforts.

"One of the most important and mistaken decisions that President Biden made was to withdraw from Bagram Air Base. Bagram Air Base is 30 or so miles north of the capital. It was a military facility. It was indeed the heart of American counterterrorism efforts in Afghanistan for years. It would have been a far better alternative for carrying out the evacuation that is now going on," Sales said. 

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Sales, a Vandenberg Coalition Advisory Board member, said that the base would have been "far better" for American evacuation efforts because it is remote, far from population centers and easier to defend and control access. Kabul's airport, on the other hand, is more dangerous and susceptible to attacks due to its location in the heart of the densely packed city center, surrounded by hotels, buildings and crowds of people.

He referenced previously reported information about how the White House, over several points during the last two weeks, was presented with opportunities to reconsider the decision to leave Bagram and each time declined to go back in. 

"I think that was probably one of the most important missteps that the White House took over the course of the evacuation," said Sales.

Sales also told Fox News that the U.S. should have extended the perimeter around the airport, and the Biden administration has not provided a good reason as to why that did not happen. 

"The United States should not be outsourcing security at the airport to the Taliban. American lives are at stake and there is no substitute to extending the security perimeter to keep our people safe."

Sales also told Fox News that the attacks near the Kabul airport Thursday were likely carried out by ISIS Khorasan Province (ISIS-K), a more local branch of the global Islamic State of Iraq (ISIS) network, signaling that terrorist threats in Afghanistan will continue to grow.

"It is very worrying that ISIS-K, if it is indeed them, has been able to carry out a sophisticated, mass casualty attack like this because it suggests that terrorist threat within Afghanistan is going to continue to grow. And it's significant because the Taliban and ISIS have been fighting against each other for years," said Sales.

"If it was them, the fact that ISIS was able to carry out a sophisticated attack like this, despite Taliban pressure against them, really suggests that Afghanistan going forward is going to be a petri dish for all kinds of terrorist threats."

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Sales referred to an attack on a maternity hospital in Afghanistan carried out by ISIS-K last year, targeting nurses, doctors, mothers and newborn children as an example of how "utterly barbaric and depraved" the terrorist organization is.

When asked by Fox News about how ISIS-K was able to quickly pull off such a sophisticated attack, Sales said that, although it is premature to draw any firm conclusions, one possibility is that ISIS capability in the region enhanced after fighters who were in prison were freed as the Taliban took power after U.S. and NATO troops withdrew.

"I think one of the things we'll need to look at is the extent to which escaped ISIS prisoners had a role in planning and carrying out this attack."

Sales said it is hard to say if ISIS-K will carry out another attack, but they have shown the world what that they are capable of carrying out a mass casualty attack. "A group that can do it once is a group that can do it twice," he stated.

Sales also warned that the only way the U.S. was able to warn Americans about the threat of a possible attack, in the days leading to Thursday's bombing, was because we have troops on the ground collecting intelligence. 

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"The moment the last C-17 takes off, and we leave the country behind with no military or diplomatic presence on the ground, our ability to collect information about plots like the one that unfolded today is going to be dramatically reduced."

Sales said that the White House needs to quickly figure out how to evacuate the roughly 1,000 Americans that remain in Afghanistan since the Kabul airport is not sufficiently secure.