WASHINGTON (AP) — A world away from the evacuation violence in Afghanistan, President Joe Biden was meeting Thursday with a bipartisan group of governors from across the U.S. who have said they want to help resettle Afghans fleeing their now Taliban-ruled country.

The White House meeting was taking place days before a Tuesday deadline for the U.S. to halt evacuations of Americans and vulnerable Afghans from the airport in Kabul, and to withdraw from the country entirely after 20 years of engagement.

Some governors have said they want to help temporarily house or resettle Afghans in their communities because many aided the U.S. war effort and now fear retribution from the Taliban for that assistance. Officials say the U.S. must keep its word to help these Afghans.

But some conservatives have been sounding alarms about a new influx of refugees to the U.S., coming on top of large groups of Central American migrants and unaccompanied children trying to enter the U.S. through the border with Mexico.

There are also concerns that some refugees coming from Afghanistan might actually be terrorists, though the administration says all are being screened.

Maryland Gov. Larry Hogan, a Republican, is among those who say assisting Afghan refugees is paramount, even as he has criticized Biden's handling of the U.S. pullout from Afghanistan,.

“We made a commitment. We can't let them down,” Hogan said this week on “CBS This Morning.” “What kind of message does it send to our allies across the world if our word is no good.”

Separately Thursday, an explosion went off outside the airport in Kabul, the capital, where thousands of people have flocked as they try to flee Afghanistan. Officials offered no casualty count, but a witness said several people appeared to have been killed or wounded.

The explosion detonated as the U.S. works to get remaining Americans out of the country. Secretary of State Antony Blinken said Wednesday that as many as 1,500 Americans may be awaiting evacuation amid growing warnings of terrorist threats targeting the airport.

Asked during an interview with ABC News about reports the evacuation could end on Friday, Ross Wilson, the U.S. ambassador to Afghanistan, declined to comment. He said “there are safe ways to get to” the airport for those Americans who still want to leave. He added that “there undoubtedly will be” some at-risk Afghans who will not get out before Biden's deadline.

The airlift continued Thursday despite warnings of vehicle-borne bomb threats near the airport. The White House said 13,400 people had been evacuated in the 24 hours that ended early Thursday morning Washington time. Those included 5,100 people aboard U.S. military planes and 8,300 on coalition and partner aircraft. That was a substantial drop from the 19,000 airlifted by all means the day before.

Several of the Americans working phones and trying to get out former Afghan colleagues, women's advocates, journalists and other vulnerable Afghans said they were still waiting for U.S. action.

“It’s 100% up to the Afghans to take these risks and try to fight their way out,” said Sunil Varghese, policy director with the International Refugee Assistance Project.

Blinken emphasized at a State Department briefing on Wednesday that “ evacuating Americans is our top priority. ”

He added: “We’re also committed to getting out as many Afghans at-risk as we can before the 31st," when Biden plans to pull out the last of thousands of American troops.

As more nations began shutting down own evacuation flights and pulling out before the U.S. withdrawal, there were new European warnings about the threats. British Armed Forces Minister James Heappey told the BBC that there was ”very, very credible reporting of an imminent attack” at the airport, possibly within hours.

The U.S. Embassy in Kabul, the capital, issued a security alert Wednesday warning American citizens away from three specific airport gates. Senior U.S. officials said the warning was related to ongoing and specific threats involving the Islamic State and potential vehicle bombs.

Blinken said the State Department estimates there were about 6,000 Americans wanting to leave Afghanistan when the airlift began Aug. 14, as the Taliban took the capital after a stunning military conquest. About 4,500 Americans have been evacuated so far, Blinken said, and among the rest “some are understandably very scared.”

The 6,000 figure is the first firm estimate by the State Department of how many Americans were seeking to get out. U.S. officials early in the evacuation estimated as many as 15,000, including dual citizens, lived in Afghanistan. The figure does not include U.S. Green Card holders.

About 500 Americans have been contacted with instructions on when and how to get to the chaotic Kabul airport to catch evacuation flights.

In addition, 1,000 or perhaps fewer are being contacted to determine whether they still want to leave. Blinken said some of these may already have left the country, some may want to remain and some may not actually be American citizens.

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Associated Press writers Darlene Superville and Lolita C. Baldor in Washington and James LaPorta in Boca Raton, Florida, contributed to this report.