President Joe Biden was warned Friday that another terror attack in Kabul is “likely,” one day after a suicide bomber outside the city’s airport killed at least 113 people, including 13 U.S. service members.

The stark warning from the president’s national security team came as the United States entered the final days of a monthslong military withdrawal from Afghanistan, on track to meet Biden’s Aug. 31 deadline for a full withdrawal.

In the two weeks since Kabul fell on Aug. 15, U.S. and coalition partners have facilitated the evacuation of more than 100,000 people, including more than 5,000 American citizens. The Pentagon said Friday that more than 5,000 U.S. service members are on the ground in Kabul assisting with the evacuation efforts.

“The next few days of this mission will be the most dangerous period to date,” they told Biden, according to a White House statement.

In response, Biden reaffirmed his “approval of all authorities they need to conduct the operation and protect our troops,” said the White House.