The Special Immigrant Visa program is available to Afghans who worked with the U.S. troops or NATO during their time in Afghanistan, either as interpreters or in other roles, the AP reported. Afghans who are deemed as especially susceptible to danger from the Taliban, including journalists and people employed by nongovernmental organizations, were also able to apply for the program.

Mayorkas, who along with his family arrived in the U.S. as a refugee from Cuba, asserted the United States’ duty to shield Afghan allies, the AP reported.

“We have a moral imperative to protect them, to support those who have supported this nation,” Mayorkas said.

For more reporting from the Associated Press, see below.

At least 50,000 Afghans are expected to be admitted into the United States following the fall of Kabul as part of an “enduring commitment” to help people who aided the American war effort and others who are particularly vulnerable under Taliban rule, Mayorkas said Friday.

Tens of thousands of Afghans have already made it through security vetting and arrived in the U.S. to begin the process of resettlement. Exactly how many more will come and how long it will take remain open questions, Mayorkas said as he outlined the effort.

“Our commitment is an enduring one,” he told reporters. “This is not just a matter of the next several weeks. We will not rest until we have accomplished the ultimate goal.”

Mayorkas and other Biden administration officials are providing the most detailed look to date at what began as a frantic and chaotic effort to evacuate U.S. citizens, permanent residents and Afghans before the August 30 withdrawal of American troops and the end of the country’s longest war.

Nearly 130,000 were airlifted out of Afghanistan in one of the largest mass evacuations in U.S. history. Many of those people are still in transit, undergoing security vetting and screening in other countries, including Germany, Spain, Kuwait and Qatar.

While Mayorkas said the U.S. expected to admit at least 50,000 Afghans, he suggested there was no set limit or a specific time frame.

“Our mission is not accomplished until we have safely evacuated all U.S. citizens who wish to leave Afghanistan or lawful permanent residents, all individuals who have assisted the United States in Afghanistan,” he said. “This effort will not end until we achieve that goal.”

Though the U.S. airlift has ended, Taliban officials have said they would allow people with valid travel papers to leave, and they may feel compelled not to backtrack as they seek to continue receiving foreign aid and run the government.

Most of the Afghans who have arrived in the U.S. are being housed on military bases around the country, receiving medical treatment, assistance with submitting immigration applications and other services aimed at helping them settle in the country.