KABUL, Afghanistan — For years, Hamid Karzai International Airport has been a main gateway to Afghanistan, an aspirational symbol of civilian life and normalcy amid military bases, warplanes and the scars of decades of fighting in the surrounding countryside.
But now the airport, known to all as Kabul International, has become the last stand in America’s 20-year campaign in Afghanistan.
If the United States and its allies can complete a deal for Turkey to keep forces in place to secure the airport, President Biden can go ahead with his plan to maintain the American Embassy — and diplomatic missions from allied countries — even after combat troops for the United States and the North Atlantic Treaty Organization depart.
If not, senior American and NATO officials said, the consequences could be substantial: Mr. Biden’s plans to try to retain a diplomatic presence in the country, as part of an international effort seeking to prevent a return to the grim Taliban-controlled era of the past, will most likely be cast aside, and access to the country by aid groups could be cut off.
“Security at the airport in whatever form or fashion it takes will be important, not only for the United States, but for any other nation that likewise plans to maintain a diplomatic presence in Kabul,” the Pentagon spokesman, John F. Kirby, said in an interview.
James G. Stavridis, a retired admiral who served as the North Atlantic Treaty Organization’s supreme allied commander for Europe, put it more bluntly. “Without a secure airport, the ability to conduct day-to-day embassy operations in a large country like Afghanistan, which is the size of Texas, is significantly diminished,” he said.
“In addition to personal safety and ability to evacuate in emergencies, helos and planes are needed to move U.S. diplomats, aid workers, intelligence officers and support personnel around the country,” he said. “Without that fundamental capability, the mission of the embassy is a failure.”
Turkey for its own reasons wants to retain a presence in Afghanistan, where it has a long affiliation, and a shared history and religion as well as an economic stake. As a Muslim-majority nation and a member of the Atlantic alliance, Turkey has played a consistent role in Afghanistan since 2001, including sending troops in noncombat roles. It currently has about 600 service members in Afghanistan, where its main mission has been providing security for the airport.
The talks over completing an agreement for Turkey to continue doing so have yet to resolve details of how the operation would work. They are also taking place against the backdrop of high-level strains between Turkey and the United States over issues like Ankara’s purchase of Russian antiaircraft batteries.
Military planners and intelligence analysts say the growing strength of the Taliban and planned withdrawal of international combat troops means that the Afghan government was likely to fall in six months to two years. And while it is not clear that the Taliban would want to completely shut down the airport and isolate the country if they take full control of Afghanistan, the group has signaled that it will not accept the presence of any foreign troops, even from Turkey.
After two decades of war, failed military strategies and set-piece battles that seem to have fallen out of remembered time, the fate of the airport is shaping up as a potential epitaph to America’s presence in Afghanistan.
The importance of the strip of tarmac, radars and terminals, surrounded by the ring of mountains that define the capital city, cannot be overstated. Beyond its strategic importance for maintaining embassy operations and having an evacuation route for diplomats and the forces protecting them, the airport is the gateway to Afghanistan for workers from international aid groups and other nongovernmental organizations and health care providers that remain vital in a nation long reliant on foreign assistance to provide basic services.
“It’s important for the diplomatic communities, aid agencies, international organizations and also for the country to continue to have support from outside,” Abdullah Abdullah, the chairman of the Afghan government council that has led peace negotiations with the Taliban, said of the airport in an interview on Friday after he and President Ashraf Ghani met with Mr. Biden at the White House.
Kabul International’s importance was underscored last week after Pentagon and other administration officials said the military airport at Bagram, about an hour north of Kabul, would soon close on schedule.
Administration officials had briefly considered delaying the closure of Bagram to give commanders more options if security arrangements at Kabul International stalled or Pentagon planners needed another airport to evacuate thousands of Western diplomats or Afghan interpreters and other workers who helped the United States.
“The withdrawal continues on pace,” Mr. Kirby told reporters on Thursday when asked about any plans to delay shutting Bagram.
The United States and Turkey agreed this month on the outlines of a plan for the Turks to continue providing security at the airport, easing anxiety among many allied partners about maintaining safe access to the airfield for their embassies.
Jake Sullivan, Mr. Biden’s national security adviser, told reporters this month that both sides had made a “clear commitment” on the security of the airport. But Turkey and its Atlantic alliance partners continue to haggle over the details of how this will be done, and no specifics have yet emerged.
A Pentagon team met with Turkish officials in Ankara last week to begin hammering out many of the political, financial and logistic details.
American officials say Turkey is making two broad sets of requests to continue providing security at the airport, which it has done for the past several years as part of the NATO force in the country. One set deals with the tactical details of securing the airport.
Turkey is expected to provide 600 to 1,000 troops to secure the airport, but it is looking for other nations to contribute up to an additional 1,000 troops, Pentagon officials said. Turkish officials have said they are seeking help from Hungary to provide security. Turkey’s defense minister, Hulusi Akar, has said that Turkey would not be sending additional troops to increase its contingent already in Afghanistan.
President Recep Tayyip Erdogan of Turkey has said he would also discuss Turkey’s remaining at the airport with Afghanistan’s neighbor Pakistan, which is an influential supporter of the Taliban and has good relations with Mr. Erdogan.
About 650 U.S. troops are expected to remain in Afghanistan to provide security for diplomats after the last American combat troops leave in the next weeks, American officials said on Friday.
In addition, several hundred additional American forces will remain at the Kabul airport, possibly until September, to assist the Turkish troops providing security, as a temporary move until a more formal Turkey-led security operation is in place, planning previously reported by The Associated Press.
The United States is expected to commit Black Hawk helicopters and their aircrews and maintenance specialists. The helicopters would be used to ferry diplomats from Kabul to the airport.
Washington is also expected to share intelligence with the Turks and extend the range of an antirocket system to help protect the airport, American officials said.
These tactical details are so important that Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, has personally gone through the list of requests and requirements with his Turkish counterpart, Gen. Yasar Guler, Pentagon officials said.
There are also issues with the operation of the airport, which is heavily reliant on international forces to oversee flight operations. They include the need to provide more training for Afghan air traffic controllers and replacing a contract that provides communications for the air traffic management center for the airport.
A second set of higher-level requests was conveyed by Mr. Erdogan to Mr. Biden during the NATO summit this month in Brussels.
The most vexing of half a dozen disputes between the two countries is Mr. Erdogan’s refusal to reverse his purchase of an advanced surface-to-air missile system from Russia. The deal by a North Atlantic Treaty Organization ally to buy sophisticated Russian military equipment led to Turkey becoming the only country in the alliance to be on the receiving end of U.S. sanctions and removed from the F-35 fighter aircraft program.
American officials, however, insist that any deal allowing the S-400 system to proceed as part of the deal to secure the Kabul airport is a nonstarter.
But Turkish officials have continued to bring up the issue at lower-level discussions, American officials said.
Taliban leaders have already expressed opposition to any foreign personnel, including from Turkey, remaining in the country to provide airport security.
Though the Afghan government has welcomed Turkey’s commitment to the airport, the Taliban do not, despite some far-fetched hope among Western officials that the insurgent group would allow Turkey’s presence after the Americans left.
In a statement this month, the Taliban said that “the presence of foreign forces under whatever name or by whichever country in our homeland is unacceptable for the Afghan people and the Islamic Emirate.”
Thomas Gibbons-Neff reported from Kabul, and Eric Schmitt and Helene Cooper from Washington. Carlotta Gall contributed reporting from Istanbul.