President Joe Biden warned on Saturday, Aug. 28, that another attack against U.S. forces is “highly likely” to take place in Afghanistan in the next 24 to 36 hours, before the deadline for the United States to exit the country. But he vowed a second retaliation against the perpetrators.

In a statement on the evacuation mission in Afghanistan, Biden said that the situation at the Kabul airport continues to be extremely dangerous, and the threat of terrorist attacks on the airport remains high.

“Our commanders informed me that an attack is highly likely in the next 24-36 hours,” Biden said. “I directed them to take every possible measure to prioritize force protection, and ensured that they have all the authorities, resources and plans to protect our men and women on the ground.”

The warning comes after an affiliate of the Islamic State namely ISIS-K conducted a suicide bomber at a checkpoint outside the Kabul airport on Thursday, killing 13 U.S. service members and more than 110 Afghans.

On Saturday, the U.S. military launched a drone strike in retribution, killing two members of ISIS-K in the group’s stronghold in eastern Afghanistan.

In his statement on Saturday, Biden vowed to issue another retaliatory strike against the terrorists responsible for Thursday’s attack.

“This strike was not the last. We will continue to hunt down any person involved in that heinous attack and make them pay,” Biden said. “Whenever anyone seeks to harm the United States or attack our troops, we will respond. That will never be in doubt.”

Biden said that his administration is discussing the preparations to help U.S. forces and Afghan allies continue to leave Afghanistan after the U.S. military departs.

The United States is rushing with the evacuation mission from Kabul airport before the deadline to complete a full military withdrawal by Aug. 31.