The collapse of Afghanistan's government led lawmakers and advocates to urge the Biden administration to rapidly evacuate thousands of Afghans who helped the U.S. during its lengthy war there.

The U.S. has evacuated around 2,000 applicants for the Afghan special immigrant visa program and their families, but as many as 50,000 remain in the nation now under control of the Taliban, advocates estimate. The U.S. has slots for 34,500 under its SIV program.

Garry Reid, the director of Defense Intelligence, who is leading the Defense Department's work on the evacuation, said at a news briefing Monday that plans were underway to evacuate as many as 20,000 to 22,000 additional special visa applicants, possibly to military bases such as Fort McCoy in Wisconsin and Fort Bliss in Texas.

"There may be other sites identified if services are needed, if additional capacity is needed," Reid said. "As with the operation we've been supporting at Fort Lee [in Virginia], persons that come to these locations will have been pre-screened by the Department of Homeland Security to enter on condition of full immigration processing once they arrive."

The State and Defense departments said in a joint statement Sunday they are working to evacuate "particularly vulnerable Afghan nationals." The departments also pledged to “accelerate the evacuation of thousands of Afghans eligible for U.S. Special Immigrant visas.”

The two departments said the U.S. is working to secure the airport in Kabul with the aid of nearly 6,000 troops. On Twitter, videos circulated Sunday of desperate Afghans clinging to U.S. Air Force planes flying out of Kabul in an effort to escape the country, with some falling to their deaths as the aircraft took flight.

“For all categories, Afghans who have cleared security screening will continue to be transferred directly to the United States. And we will find additional locations for those yet to be screened,” the State and Defense statement said.

For many lawmakers and immigrant advocates who have spent months sounding the alarm on the danger faced by Afghan allies in the face of a Taliban takeover, it was too little, too late.

“To say that today is anything short of a disaster would be dishonest,” said Rep. Seth Moulton, D-Mass. “America and our allies must drop the onerous visa requirements where a typo can condemn an ally to torture and death, and the military must continue the evacuation for as long as it takes.”

“The Biden administration’s blind eye to Afghan nationals is a stain on the United States,” Ali Noorani, president of the National Immigration forum, said in a statement Sunday. “What is astonishing is the utter lack of planning by the administration to develop a plan to protect the tens of thousands of Afghan nationals who worked with our military.”

The Afghan SIV program, designed to provide a safe haven for U.S. military allies in Afghanistan, has long been beleaguered by onerous requirements and wait times that stretch for years.

Last month, lawmakers authorized an additional 8,000 visa slots in a law to improve Capitol security, as well as more than $1 billion to fund the evacuation. 

State Department officials in recent weeks have cited plans to move SIV applicants who have not yet completed security vetting to third countries while their applications are processed, and to expand priority refugee pathways for Afghans who don’t qualify for the SIV program’s narrow parameters but are likely to face persecution after the U.S. withdrawal. Educators and women's rights activists are among those seen as vulnerable. 

It is not clear how the U.S. can carry out those plans in a Taliban-run country without a functional U.S. embassy.

The situation is “pretty hopeless,” said James Miervaldis, chairman of No One Left Behind, a nonprofit organization that helps SIV applicants. He and other veterans have spent months trying to rescue Afghan interpreters they worked with while they were deployed.

“Strategically, this is a disaster,” he said. “Everyone believed in the process and the systems.”