WASHINGTON (AP) — Senators from both major political parties are urging congressional leaders to ensure that more visas are made available to Afghans who worked alongside U.S. troops in America's longest war before a crucial pathway to safety in the United States abruptly closes.

In a letter obtained by The Associated Press, more than a dozen Republican and Democratic senators said Congress needs to raise the limit on the number of special immigrant visas the U.S. can process for Afghans. They said an additional 20,000 are needed before the end of the fiscal year in September.

"This critical program has already saved the lives of thousands of Afghans who served with bravery and honor alongside United States troops and diplomats in support of the mission in Afghanistan," the lawmakers, led by Sen. Jeanne Shaheen, a New Hampshire Democrat, wrote in the letter to Majority Leader Chuck Schumer, D-N.Y., and Minority Leader Mitch McConnell, R-Ky. "We must now uphold our commitment to these individuals and ensure that those qualified applicants are able to find safety in the United States."

State Department spokesman Matthew Miller also called on Congress last week to increase the visa cap, saying that it would allow the U.S. to "meet our obligation to those Afghans who put their lives on the line for the United States, make sure that they are not forgotten."

Senators included an increase in the annual cap of visas in a funding bill last year, but it's unclear whether that provision will make it into the final package lawmakers are racing to finish by the March 22 government funding deadline.

The special immigrant visa, or SIV, program allows eligible Afghans who helped Americans despite great personal risk to themselves and their loved ones to apply for entry into America with their families. Eligible Afghans include interpreters for the U.S. military as well as individuals integral to the American embassy in Kabul.

While the program has existed since 2009, the number of applicants skyrocketed after the chaotic U.S. withdrawal from Afghanistan in August 2021. With the Taliban now back in power, advocates say Afghans who helped the U.S. are often living in hiding and facing torture and death if they're found.

"Congress' inaction to honor our commitments not only undermines our national conscience but erodes the very principles America claims to stand for," said Shawn VanDiver, a Navy veteran and head of #AfghanEvac, a coalition supporting Afghan resettlement efforts. "It's high time Congress proves its integrity is more than just lip service; our Afghan allies deserve nothing less."

Since the program's inception, tens of thousands of visas have been issued to eligible Afghans, according to the State Department, with more than 30% of the total applications processed just since the withdrawal. A similar U.S. program exists for Iraqis, but both programs have come under criticism from lawmakers and advocates who say that cases move much too slowly, leaving applicants in a dangerous limbo.

It's up to Congress to set the cap on the number of visas available under the program. But when that cap is reached, Congress has had to go back periodically to increase the number of visas available.

Andrew Sullivan, the director of advocacy for No One Left Behind, which advocates for SIV applicants, said they're down to roughly 7,000 visas left and if the State Department keeps approving visas at the current rate, they could run out of visas by the end of summer.

"It's massive. It fundamentally amounts to a death knell for the program" if Congress doesn't approve more visas, Sullivan said. "You're going to have tens of thousands of people who are left behind through no fault of their own."

Advocates have previously complained about the slow pace of processing visas, but in recent months the numbers have been climbing and could hit 1,000 this month after the State Department streamlined the process for considering applications. The improvements have resulted in Afghans who helped the U.S. reaching safe harbor more quickly.

But if lawmakers fail to authorize any more visas, hundreds of thousands of Afghan allies would remain in Afghanistan, where the Taliban has labeled them and their families as traitors. Sullivan said his nonprofit has identified more than 100 people who were killed by the ruling militant group and were either SIV applicants or were likely eligible for the visa program.

Failure to approve more visas would be another disappointment for Afghans as they wait for more concrete action from Congress. A bipartisan effort to permanently provide a pathway to citizenship for Afghan allies fell apart last month, thwarted by larger disagreements between Democrats and Republicans over border policy.

"For two decades, the U.S. military mission in Afghanistan relied on trusted Afghan allies who stood shoulder-to-shoulder with American troops," Shaheen, the New Hampshire senator, said in a statement. "We promised to protect them — just as they did for us, yet they are now at grave risk as the Taliban continue to hunt for them."