WASHINGTON (AP) — President Joe Biden is pressing ahead with the evacuation of Americans and others from Afghanistan after attacks that killed at least 12 U.S. servicemembers and dashed hopes of ending the 20-year U.S. war without further bloodshed. As many as 1,000 Americans and many more Afghans are still struggling to get out of Kabul.

Biden was briefed on the attacks, which also killed dozens of Afghans and came 12 days into the rushed evacuation and five days before its scheduled completion. Some Republicans argued to extend the evacuation beyond next Tuesday's deadline.

The U.S. general overseeing the evacuation, Gen. Frank McKenzie, said after the attacks, “If we can find who is associated with this, we will go after them.” He said it would be a mistake for the United States to call an early end to the evacuation, despite the risks.

The administration has been widely blamed for a chaotic and deadly evacuation that began in earnest only after the collapse of the U.S.-based Afghan government and the Taliban's takeover of the country. More than 100,000 people have been evacuated so far.

Thursday's attacks were sure to intensify political pressure from all sides on Biden, who already was under heavy criticism for not beginning the pullout earlier. He had announced in April that he was ending the U.S. war and would have all forces out by September.

House Republican leader Kevin McCarthy of California called for Speaker Nancy Pelosi, D-Calif., to bring the chamber back into session to consider legislation that would prohibit the U.S. withdrawal until all Americans are out. That's highly unlikely, and Pelosi's office dismissed such suggestions as “empty stunts.”

At the Pentagon, Gen McKenzie said the military believes the attacks on the airport's perimeter were carried out by fighters affiliated with the Islamic State group's Afghanistan arm. He said more attempted attacks were expected.

After the suicide bomber's attack at the airport's Abbey Gate, a number of ISIS gunmen opened fire on civilians and military forces, he said. There also was an attack at or near the Baron Hotel near that gate, he said.

The attacks won't drive the U.S. out earlier than scheduled, he said.

“Let me be clear, while we are saddened by the loss of life, both U.S. and Afghan, we are continuing to execute the mission,” he said. He said there were about 5,000 evacuees on the airfield Thursday awaiting flights. He said the Taliban have been “useful to work with” and are not suspected in the attacks.

“We thought this would happen sooner or later," McKenzie said, adding that U.S. military commanders were working with Taliban commanders to prevent further attacks.

McKenzie said that in addition to the 12 U.S. service members killed in the attacks, at least 15 were injured.

As details of the attacks emerged, the White House rescheduled Biden's first in-person meeting with Israel's new prime minister and canceled a video conference with governors about Afghan refugees arriving in the United States.

Biden had pledged to get out of Afghanistan every American who wished to leave. As of Thursday, the State Department estimated there were as many as 1,000 Americans in Afghanistan who may want help getting out.

Biden on Thursday had been scheduled to host Israeli leader Naftali Bennett, who is on his first visit to the United States since taking office. The meeting was rescheduled for Friday. Biden canceled plans to meet virtually with a bipartisan group of governors who have said they want to help resettle Afghan refugees.

A number of U.S. allies said they were ending their evacuation efforts in Kabul, at least in part to give the U.S. the time it needs to wrap up its evacuation operations before getting more than 5,000 U.S. troops out by Tuesday.

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.

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. He spoke shortly before the deadly attacks.

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.

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