WASHINGTON, Aug 19 (Reuters) - The U.S. government is "laser focused" on the potential for a terrorist attack in Afghanistan by a group like ISIS-K, a sworn enemy of the Taliban, White House national security adviser Jake Sullivan told NBC Nightly News on Thursday. Sullivan told the NBC program that getting Americans out of Afghanistan was "a risky operation" given questions about whether the Taliban would continue to allow the safe passage of people to the airport and other contingencies such as possible attack by an Islamist group such as ISIS-K. "One of the contingencies we are very focused on, laser focused on, is the potential for a terrorist attack by a group like ISIS-K, which of course is a sworn enemy of the Taliban, so we will keep working to minimize the risks and maximize the number of people on planes," Sullivan said. U.S. officials say they are working around the clock to evacuate Americans and those who aided U.S. forces out of Kabul, but that the security situation on the ground is challenging given the presence of groups like ISIS-K. Sullivan told NBC it was unclear exactly how many Americans were still in the country, but the Biden administration is committed to getting any American who wants to leave and gets in contact with U.S. officials onto a plane. But he cautioned that the situation was fluid. "We right now have established contact with the Taliban to allow for the safe passage of people to the airport and that is working at the moment to get Americans and Afghans at risk to the airport," he said. "That being said, we can"t count on anything." Sullivan added that Washington would "keep working to minimize the risks and maximize the number of people on planes." Islamic State Khorasan, also known as IS-K or ISIS-K, remains active three years after its inception, according to the Center for Strategic and International Studies, which said the group received support from Islamic State in Iraq and Syria. CSIS said the group was responsible for nearly 100 attacks against civilians in Afghanistan and Pakistan, as well as roughly 250 clashes with the U.S., Afghan, and Pakistani security forces since January 2017. Reporting by Andrea Shalal, Editing by Rosalba O"Brien Our Standards: The Thomson Reuters Trust Principles.