Maine Sens. Susan Collins, a Republican, and Angus King, an independent who caucuses with Democrats, are seen in this April 2018 file photo. Credit: Andrew Harnik / AP

More than 50 U.S. senators including Susan Collins and Angus King are calling on President Joe Biden’s administration to do more to assist Afghan allies fleeing the country following the Taliban takeover this past weekend.

In a letter to Biden, the group, which included 10 Republicans and 41 Democrats along with King and Sen. Bernie Sanders, I-Vermont, calls on his administration to speed up visa processing and help Afghan citizens still in the country who may be at risk.

Afghans who assisted the U.S. military during its nearly 20-year occupation of the country are often eligible for visas that allow them and their families to immigrate to the U.S. But the program has a long backlog, leaving many who aided U.S. troops now vulnerable to retribution.

“The Taliban’s rapid ascendancy across Afghanistan and takeover of Kabul should not cause us to break our promise to the Afghans who helped us operate over the past twenty years and are counting on us for assistance,” the senators wrote. “American inaction would ensure they become refugees or prime targets for Taliban retribution.”

The group calls on Biden to immediately implement a law cosponsored by King to expand eligibility for the Special Immigrant Visa program and allow the U.S. to immediately issue visas to those who have completed necessary steps outside of a medical exam, among other things.

The senators also said the U.S. military should assist Afghans who need transport from other parts of the country to Kabul, the sole site for military evacuations, and consider how to help those who may not have the proper documents if they had to flee quickly.

King, an independent who caucuses with the Democrats, has pushed on the issue of visas for Afghan citizens for the past several months, saying in a floor speech in June that the U.S. had a “​​moral and ethical obligation,” as well as a national security interest, in providing for the safety of interpreters and others who assisted the U.S. military. Other members of Maine’s congressional delegation have also been supportive of the effort.

About 100,000 Afghan citizens may be seeking evacuation from the country due to their work with the U.S. military, according to one nonprofit. U.S. officials said late Thursday they had evacuated around 6,000 people — including both American and Afghan citizens — from Kabul in the past few days and are continuing to ramp up capacity.