President Biden is expected to defend his decision on Afghanistan when he speaks at 2:45 p.m. from the White House -- a day after the last U.S. troops left in accordance with his self-imposed deadline but also while other Americans who wanted to leave were left behind to deal with an uncertain fate.

In an exclusive interview with George Stephanopoulos on ABC's "Good Morning America," Biden's national security adviser Jake Sullivan offered more defense for the administration's handling of the Afghanistan withdrawal, perhaps foreshadowing Biden's remarks this afternoon.

Though Stephanopoulos pressed him for details on the plan to evacuate the remaining Americans, which Secretary of State Antony Blinken said is "under 200," Sullivan repeated they will use "every available diplomatic means with the economic leverage that we have," but he did attempt to take credit for the successful evacuations -- and even pinned some of the blame on the remaining Americans who weren't able to make it out.

"We got out between 5,500 and 6,000 people -- Americans from Afghanistan -- we got out 97 or 98% of those on the ground and the small number who remain, we contacted repeatedly over the course of two weeks to come to the airport to come to a rally point. 5,500 or more did that," Sullivan said.

In response to criticism from many Republicans lawmakers like Arkansas Sen. Tom Cotton, Sullivan contended that only the president, as commander in chief, knows what it is to make these hard decisions.

"Those criticizing are not the ones who have to sit in the Situation Room and make the hard calls about the threats that we face and the objectives we're trying to obtain and President Biden made that hard call and it is a call he believes will ultimately serve the interests of our people, all of our citizens and our country," he said.

He also insisted aid will not be given to the Taliban unless they adhere to international obligations.

"It will be about whether they follow through on their commitments, their commitments to safe passage for Americans and Afghan allies. Their commitment to not allow Afghanistan to be a base from which terrorists can attack the United States or any other country," Sullivan said.

-ABC News' Sarah Kolinovsky

Moments after the last U.S. troops took withdrew from Afghanistan, Taliban fighters entered the Kabul airport, wielding American-supplied weapons, equipment and even uniforms.

U.S. Army Maj. Gen. Chris Donahue, of the 82nd Airborne Division, was the last American service member to depart Afghanistan, according to Gen. Kenneth McKenzie, the commander of U.S. Central Command.

"On the last plane out was General Chris Donahue, the commander of the 82nd Airborne Division and my ground commander, and he was accompanied by our -- our charge d'affaires, Ambassador Ross Wilson, so they came out together," McKenzie said at the Pentagon briefing. "So the state and defense team came out on the last aircraft and were in fact the last people to step on the ground."

Secretary of State Antony Blinken said the U.S. will continue to engage the Taliban going forward -- engagement that will be "driven by one thing only -- our vital national interest."

"The Taliban seeks international legitimacy and support. Our message is any legitimacy and any support will have to be earned," he said. "The Taliban can do that by meeting commitments and obligations on freedom of travel; respecting the basic rights of the Afghan people, including women and minorities; upholding its commitments on counter-terrorism; not carrying out reprisal violence against those who choose to stay in Afghanistan; and forming an inclusive government that can meet the needs and reflect the aspirations of the Afghan people."

But the Taliban have already violated many of those -- denying freedom of travel to some, violating their commitments on counter-terrorism, carrying out reprisal violence and more.