WASHINGTON (AP) — Secretary of State Antony Blinken said Wednesday that as many as 1,500 Americans may be awaiting evacuation from Afghanistan, a figure that suggests this part of the U.S.-led airlift could be completed before President Joe Biden’s Tuesday deadline. Untold thousands of at-risk Afghans, however, are struggling to get into the Kabul airport.

Blinken said the State Department estimates there were about 6,000 Americans who wanted to leave Afghanistan when the airlift began Aug. 14, and that about 4,500 of them have been evacuated so far. The 6,000 figure is the first public estimate by the State Department of how many Americans were seeking to get out when the Taliban completed its takeover of Afghanistan.

“Some are understandably very scared,” Blinken told a State Department news conference.

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.

Of the 1,000, the number who are “actively seeking assistance” to leave Afghanistan “is lower — likely significantly lower,” Blinken said.

The Biden administration has stressed that American evacuees are its first priority, even as it attempts also to airlift Afghans who worked for the U.S. government or military or to build Afghan civil society during the 20-year war as well as what it calls “vulnerable Afghans” — those who believe they face retribution from the Taliban for their role in opposing the insurgency.

The Tuesday deadline aside, Blinken said, "There is no deadline on our work to help any remaining American citizens who decide they want to leave to do so, along with the many Afghans who have stood by us over these many years, and want to leave, and have been unable to do so. That effort will continue, every day, past August 31.”

Biden said Tuesday he has asked his national security team for contingency plans in case he decides to extend the deadline.

The U.S. Embassy in Kabul has been evacuated; staff are operating from the Kabul airport and are to leave by Aug. 31.

However, refugee groups are describing a different picture when it comes to many Afghans: a disorganized, barely-there U.S. evacuation effort for Afghan allies that leaves the most desperate to risk beatings and death at Taliban checkpoints

Some Afghans are reported being turned away from the Kabul airport by American forces controlling the gates, despite having approval for flights.

“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. “Those with young children and pregnant are willing to take those beatings to get out."

His group is one of several working with the U.S. government, and communicating with clients and colleagues on the ground, to get out those Afghans most in danger from the Taliban. Those include Afghans who formerly worked with Americans, as well as journalists, women’s rights advocates and others.

Just days are left before the U.S. military is to start shutting down its anchoring role in a massive operation that the White House says has evacuated 82,300 Afghans, Americans and other foreigners on a mix of U.S., international and private flights. The withdrawal comes under a 2020 deal negotiated by President Donald Trump with the Taliban.

Taliban leaders who took control of Afghanistan this month say they will not tolerate any extensions to the Tuesday deadline. But Taliban spokesman Suhail Shaheen tweeted that “people with legal documents” will still be able to fly out via commercial flights after Tuesday.

U.S.-based organizations, speaking on background to discuss sensitive matters, cite accounts from witnesses on the ground as saying some American citizens, and family members of Afghans with green cards, still are having trouble pushing and talking their way into the Kabul airport for flights.

Kirby said the U.S. military will preserve as much airlift capacity at the airport as possible in the coming days, ahead of Tuesday's deadline. The military will “continue to evacuate needed populations all the way to the end,” he said. He added that in the final days and hours there will have to be a balance in getting out evacuees as well as U.S. troops and their equipment.

Maj. Gen. Hank Taylor, the deputy director of regional operations for the Joint Chiefs of Staff, said U.S. forces had conducted another helicopter mission beyond the perimeter of the airport to pick up people seeking to evacuate.

He said the operation happened in Kabul during the night and that the people were now safely at the airport awaiting an evacuation flight.

Taylor provided no other details, but Germany’s top military commander, Gen. Eberhard Zorn, said separately that 21 German citizens had been extracted by the U.S. helicopter. He said the helicopter crew was American and that German troops picked up the evacuees.

In White House news conferences and remarks during the airlift, Biden has offered varying degrees of commitment to getting former Afghan translators and others most at risk from the Taliban included in the airlift.

U.S. military and diplomatic officials appear to still be compiling a list of eligible Afghans but have yet to disclose how — and how many — they may be getting out, private Americans and American organizations said.

“We still have 1,200 Afghans with visas that are outside the airport and haven’t got in,” said James Miervaldis with No One Left Behind, one of dozens of veterans groups working to get out Afghans who worked with the U.S. military during America's nearly 20 years of combat there. “We’re waiting to hear from the US. government and haven’t heard yet.”

Marina LeGree of Ascend, a U.S.-based nonprofit that worked to develop fitness and leadership in Afghan girls and young women, described getting calls from U.S. officials telling the group’s interns and staffers to go to the airport for evacuation flights, only to be turned away by American forces keeping gates closed against the throngs outside.

One Afghan intern who went to the airport with her family saw a person killed in front of them, and a female colleague was burned by a caustic agent fired at the crowd, LeGree said.

“It’s heartbreaking to see my government fail so badly,” said LeGree, the group’s American director, who is in Italy but in close contact with those in Kabul.

The number of U.S. troops at the airport has dropped by about 400, to 5,400, but the final withdrawal has not begun, Kirby said Wednesday.

He said Defense Secretary Lloyd Austin will consult directly with Gen. Frank McKenzie, the head of Central Command and overseer of the evacuation operation, before McKenzie moves ahead with the final withdrawal.