WASHINGTON — The White House hurriedly put off President Joe Biden’s first in-person meeting with Israel’s new prime minister and a phone call with governors on incoming Afghan refugees Thursday after more than a dozen people were killed in explosions outside the airport in the Afghan capital, where throngs of people are scrambling to get to planes and evacuate.

Biden was to host Naftali Bennett, Israel’s new prime minister, who is on his first visit to the U.S. since taking office. Biden also planned to meet virtually with a bipartisan group of governors who have said they want to help resettle Afghan refugees fleeing their now Taliban-ruled country.

But deadly developments in the Afghan capital of Kabul forced the White House to tear up the president’s schedule, as he monitored the airport situation that was prompted by the Tuesday deadline he set for removing American citizens and troops from Afghanistan.

Biden’s Meetings Delayed Amid Attacks in Kabul

Biden’s meetings with Bennett were delayed indefinitely, while the governors’ meeting was canceled, the White House said. A regular briefing by government health and medical experts, scheduled for Thursday, also was postponed.

Two suicide bombers and gunmen targeted crowds massing near the Kabul airport Thursday, in the final days of a massive airlift that has drawn thousands of people seeking to flee the Taliban takeover of Afghanistan.

A U.S. official said the attack was “definitely believed” to have been carried out by the Islamic State group, whose affiliate in Afghanistan grew out of disaffected Taliban members who hold an even more extreme view of Islam.

Despite intense pressure to extend the Tuesday deadline, Biden has repeatedly cited the threat of terrorist attacks against civilians and U.S. service members as a reason to keep to his plan.

A U.S. official said U.S. military members were among the wounded. The official spoke on condition of anonymity to discuss ongoing operations.

Pressure Grows to Evacuate Remaining Americans

The explosions detonated as the U.S. worked 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.

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.

Wilson 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.

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.

Number of Americans Still in Afghanistan is Unclear

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.