The United States has the capacity to evacuate the approximately 300 U.S. citizens remaining in Afghanistan who want to leave before President Joe Biden’s Tuesday deadline, senior Biden administration officials said Sunday, as another US drone strike against suspected IS militants, underscored the grave threat in the war’s final days.

“This is the most dangerous time in an already extraordinarily dangerous mission these last couple of days,” America’s top diplomat, Secretary of State Antony Blinken, said not long before confirmation of that airstrike in Kabul, the capital.

The evacuation flow of Americans kept pace even as a new State Department security alert, issued hours before the military action, instructed people to leave the airport area immediately “due to a specific, credible threat.”

Biden’s national security adviser, Jake Sullivan, said that for those U.S. citizens seeking immediately to leave Afghanistan by the looming 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.”

Sullivan said the U.S. does not currently plan to have an ongoing embassy presence after the final U.S. troop withdrawal. But he pledged the U.S. “will make sure there is safe passage for any American citizen, any legal permanent resident” after Tuesday, as well as for “those Afghans who helped us.” But untold numbers of vulnerable Afghans, fearful of a return to the brutality of pre-2001 Taliban rule, are likely to be left behind.

Blinken said the U.S. was working with other countries in the region to either keep the Kabul airport open after Tuesday or to reopen it “in a timely fashion.”

He also said that while the airport is critical, “there are other ways to leave Afghanistan, including by road and many countries border Afghanistan.” The U.S., he said, is “making sure that we have in place all of the necessary tools and means to facilitate the travel for those who seek to leave Afghanistan” after Tuesday.