Advocates estimate the total number of evacuees under the SIV program at between 50,000 and 80,000 when family members are included.
James Miervaldis, chairman of the board of No One Left Behind, an organization that helps SIV applicants get to the United States, said there now appeared to be little chance that most of the SIV applicants will be evacuated.
"The math and the timeline just do not add up ... Those people are not going to be able to leave," said Miervaldis, an Army Reserve non-commissioned officer who served in Iraq and Afghanistan.
The issue has been closely watched by lawmakers in Congress, including Biden's allies.
"We have to follow through on our promises to the thousands of Afghans who risked their lives to help us. It's time for the Biden (administration) to cut the red tape and get this done," said Democratic congresswoman Sara Jacobs.