Approximately 300 American citizens remain in Afghanistan who want to leave before President Joe Biden's Tuesday deadline for evacuations, national security adviser Jake Sullivan said on Sunday. This comes as the president warned of another terrorist attack after last week's suicide bombing at the Kabul airport that killed scores of Afghans and 13 US servicemen.

Sullivan told CBS' 'Face the Nation' for those U.S. citizens seeking to leave Afghanistan by Biden's deadline, "we have the capacity to have 300 Americans, which is roughly the number we think are remaining, come to the airport and get on planes in the time that is remaining. We moved out more than that number just yesterday. So from our point of view, there is an opportunity right now for American citizens to come, to be admitted to the airport and to be evacuated safely and effectively."

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Sullivan added that Washington has shown that it is capable of "suppressing the terrorism threat ... without a large permanent presence on the ground. ... And we will do that in Afghanistan as well as we go forward."

Islamic extremist group ISIS-K claimed responsibility for Thursday's suicide attack at Kabul airport. The US struck back at the terror outfit with a drone strike that killed two 'high profile' ISIS targets. 

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Confirming the drone attack, Capt Bill Urban, spokesperson of US Central Command, had said , "US military forces conducted an over-the-horizon counterterrorism operation today against an ISIS-K planner. The unmanned airstrike occurred in the Nangahar province of Afghanistan. Initial indications are that we killed the target. We know of no civilian casualties." 

Warning ISIS-K, US President Joe Biden on Saturday vowed to keep up airstrikes against them while also outlining the threat of another "highly likely" terror attack this weekend.

"This strike was not the last. We will continue to hunt down any person involved in that heinous attack and make them pay," he said in a statement.