With the Afghan government and military no longer able to provide cover, President Biden risks the ugliest of exits from Kabul if he blows past his promise to leave Aug. 31.

Why it matters: The Taliban now controls the area around Kabul's airport. As the U.S. removes its final 5,800 troops — and shrinks the security perimeter they've been providing — the surest way to ensure the last soldiers and diplomats get out safely is through the grace of a grisly enemy.

The big picture: A Taliban spokesman on Tuesday repeated the group's stance that it will not recognize any extension past Aug. 31. That cold reality explains why Biden is sticking to his timetable, despite pleas from allies like the United Kingdom, combat veterans and outside groups trying to evacuate Afghans.

• "Who wants to be the last man there?" a U.S. veteran nearly killed in Afghanistan told Axios.
• Biden said Tuesday the U.S. is on pace to exit by his deadline, but that will depend to the end on the Taliban's continued cooperation, including access to the airport and no disruptions to the U.S. operations.
• Secretary of State Tony Blinken tweeted twice on Tuesday about his calls to the NATO secretary general and Turkish foreign minister. Both NATO and Turkish forces have the potential to provide cover for departing U.S. forces.

The U.S. had about 2,500 troops in Kabul as of last month, with long- term plans to maintain a force to 650 Marines to protect the U.S. embassy.

• When the government collapsed on Aug. 15, the Taliban encircled the lifeline out — Hamid Karzai International Airport.
• President Biden sent in nearly 6,000 troops, and they've established a buffer and allowed its lone runway to re-open for evacuation flights.
• Nonetheless, Taliban fighters operate their own checkpoints within eyesight of the Americans, and they could shut down the airport by firing mortars into the runway or tarmacs, or by shooting at departing airplanes.

Biden has committed to leaving by Aug. 31, but White House press secretary Jen Psaki said in a statement Tuesday: "The president has asked the Pentagon and the State Department for contingency plans to adjust the timeline should that become necessary."

• CIA Director William Burns met with Taliban leader Abdul Ghani Baradar in Kabul on Monday, and Defense Department spokesperson John Kirby said on Tuesday that consultations continue.
• In his speech late Tuesday, the president noted the Taliban itself could be attacked by ISIS-K, a bitter enemy of both parties.
• "Every day we're on the ground is another day we know that ISIS-K is seeking to target the airport," Biden said.

What's next: Kirby acknowledged the risks as U.S. forces move toward the last outbound airplanes.

• Not only soldiers but State Department employees who've been processing the evacuees would be on those final flights. There would be no U.S. troops left in Afghanistan to safeguard them when the last plane departed.
• "It is all done in a very careful, methodical way, so that you can preserve as much capability to the very end that you need," Kirby said. The U.S. would try "to get our materiel out with our people," he added, referring to its last weaponry.
• If it can't fit, it will be destroyed, potentially by Air Force fighters and bombers that can shoot from a safe distance.