WASHINGTON (AP) — Tissue holders sit atop the conference table where the congressman's aides field frantic requests from constituents desperate for help in getting friends and loved ones out of Afghanistan before it's too late.

The stories have poured in by the thousands with heartbreaking pleas not to be left behind.

The tissues are used for crying breaks, one of the aides explained.

“The hardest part is just the sense of helplessness," said Rep. Eric Swalwell, D-Calif. “We’re seeing all of this, you know, anxiety, and we can’t do enough.”

Across the county, the offices of members of Congress have become makeshift crisis centers, flooded with requests for help getting people onto one of the last flights leaving the Kabul airport before President Joe Biden’s Tuesday deadline for the withdrawal of all U.S. military forces out of Afghanistan.

More than 109,000 people have been evacuated since the Taliban takeover Aug. 14, in one of the largest U.S. airlifts in history. The work could hardly be more urgent or dangerous, as Thursday's suicide bombing attack killing 13 U.S. service member and injuring 18 demonstrated. Some 169 Afghans were also killed and scores more wounded.

Biden said after the devastating attack that the U.S. would not be intimidated, “and our mission will go on." But he also acknowledged the limits of what can be done as the U.S. focuses on safe passage for Americans, while countless others remain, many fearful for their futures.

“Getting every single person out is — can’t be guaranteed of anybody," Biden said.

In the race against time, the lawmakers are stepping up where the other branches of the U.S. government have maxed out. It’s infuriating, emotional work, the rare undertaking that crosses party lines, Republicans and Democrats working around the clock to help the friends, families and loved ones of their constituents — and helping the U.S. keep its word.

In Northern Virginia, the office of Democratic Rep. Don Beyer reports that the number of constituent requests coming in — more than 100 a day — is what they would typically have in a full month. The area is home to many Afghans as well as military personnel and defense contractors, some with ties to the region. In the adjacent congressional district, the office of Democratic Rep. Gerry Connolly reports that staff has submitted the names of nearly 10,000 Americans and Afghan interpreters and others to the State Department for consideration.

Swalwell’s district is home to a large Afghan diaspora community. The city of Fremont has a neighborhood called Little Kabul. But from coast to coast, and across the heartland, lawmakers around the country are also seeing huge spikes in requests for help.

Nebraska Republican Rep. Don Bacon said his office is working with more than 800 people seeking to get out of Afghanistan — a workload that grew in part because of the number of veterans working for him, including two retired colonels plus a Gold Star wife whose husband was killed in Afghanistan, who still have connections overseas. They are having some success, but more often than not, they are hearing from people who can't get through Taliban-controlled checkpoints, he said.

“When you're working 18 hours a day or so for a week and people are not getting through and you hear about people dying, yeah, it's emotional," said Bacon, who served in Iraq. “These guys are on the edge of their nerves."

Rep. Michael McCaul of Texas, the ranking Republican on the House Foreign Affairs Committee, said many lawmakers are forwarding cases his way. “I get texts every night, every hour, every half-hour,” McCaul said.

The effort is personal for those members of Congress who served in the national security apparatus in Iraq and Afghanistan. Prior to joining Congress, Rep. Andy Kim, D-N.J., had provided strategic advice to Gen. David Petraeus, the former commander of U.S. forces in Afghanistan. He said his office has received more than 6,000 evacuation cases in just more than a week.

“This is about the expectation of what the American handshake means to those that were willing to put their lives at risk to help us and our service members and our diplomats on the ground,” Kim said.

In North Carolina, which is home to Fort Bragg, Republican Sen. Thom Tillis has been working with veterans from the 82nd Airborne to help people he said they consider “brothers and sisters” in arms, having worked alongside the U.S. troops for years.

“They’ve seen their families grow up, they spent time on the battlefield, they saw people die there,” Tillis said.

Tillis pushed back against those critics, particularly in his own Republican Party, who warn against welcoming the foreigners out of fears they could be terrorists themselves. “You probably ought to get to know them, maybe get to know their story and welcome them to this country,” he said. “We owe them a debt of gratitude for saving American lives.”

On Thursday, he said his office has a list of 1,000 people in Afghanistan he’s trying to help evacuate — and he’s just one senator out of 100.

“Focus on the math,” he said. ”That’s one office, and it’s growing every single day. ... It’s fairly easy to see how the number gets up in the tens of thousands.”

For all the horror stories lawmakers are hearing about people being turned away or having their papers ripped, they are getting word of some successes. Bacon said his team helped arrange for the rescue of an American family by helicopter, plus the evacuation of an Afghan general and his family.

“Our folks can know that, for the rest of their lives, they made a lifetime impact on a family," Bacon said. “They can cherish that until the day they die."

Swalwell beamed at the photo of one little smiling Afghan girl who made it out safely. “That's what keeps us going," he said.

“It's like one photo of joy for hundreds of stories that are painful and may not have a happy ending."

Kevin Freking And Lisa Mascaro, The Associated Press