It had been increasingly clear that President Joe Biden was not going to abide by the May 1 deadline agreed by his predecessor, and U.S. officials said Tuesday that the president has decided to set a new deadline of Sept. 11, 2021, for the withdrawal of U.S. troops from Afghanistan, exactly 20 years after al-Qaida's attacks triggered America's longest war.

The decision defies a May 1 deadline for full withdrawal under a peace agreement the Trump administration reached with the Taliban last year. However, Biden has been hinting for weeks that he was going to let the deadline lapse, and as the days went by it became clear that an orderly withdrawal of the remaining 2,500 troops would be difficult and was unlikely.

A senior administration official said the drawdown would begin May 1. Biden's choice of the 9/11 date underscores the reason that U.S. troops were in Afghanistan to begin with, to prevent extremist groups like al-Qaida from establishing a foothold again that could be used to launch attacks against the U.S.

The president decided that the deadline for withdrawal of U.S. forces had to be absolute, rather than provisional on conditions inside Afghanistan as the deadline neared, the senior administration official said, reported The Associated Press (AP).

"We’re committing today to going to zero" U.S. forces by Sept. 11, and possibly well before, the official said, adding that Biden concluded that a conditioned withdrawal would be "a recipe for staying in Afghanistan forever."

U.S. officials provided details on Biden’s decision on the condition of anonymity, speaking ahead of the announcement. It was first reported by The Washington Post. According to the administration official, the only U.S. forces remaining in Afghanistan will be those deemed necessary to protect diplomats in the country. An exact number had yet to be decided.

Meanwhile, Biden will address the nation Wednesday on his plans, Press Secretary Jen Psaki said Tuesday.

"The president will deliver remarks tomorrow at the White House on the way forward in Afghanistan, including his plans and timeline for withdrawing," Psaki told reporters.

"The president has been consistent in his view that there's not a military solution to Afghanistan, that we have been there for far too long," she said, as quoted by Agence France-Presse (AFP).

The extended timeline will allow a safe and orderly withdrawal of American troops in coordination with NATO allies, the administration official added. Biden's decision risks retaliation by the Taliban on U.S. and Afghan forces, possibly escalating the 20-year war, and it will reignite political division over U.S.' involvement in what many have called the endless war.

Meanwhile, NATO defense and foreign ministers will hold a videoconference Wednesday after the U.S. decision to extend the withdrawal period. The alliance announced the jumbo meeting with U.S. Secretary of State Antony Blinken and Defense Secretary Lloyd Austin attending in person after talks with NATO chief Jens Stoltenberg.

NATO allies had been waiting on Biden to make a decision on the withdrawal for some time. The other alliance members have said they would not remain in Afghanistan without U.S. troops there. "Allies have been closely consulting on the way forward in Afghanistan for many months," a NATO official told AFP.

On Wednesday, Stoltenberg "will discuss Afghanistan, as well as other issues, including Russia's aggressive actions and preparations for the upcoming NATO summit," with Blinken and Austin, ahead of the virtual NATO ministers' meeting, the official said.

A U.S. intelligence community report issued Tuesday about global challenges for the next year said prospects for a peace deal in Afghanistan are "low" and warned that "the Taliban is likely to make gains on the battlefield."

If the coalition withdraws support, the report says, the Afghan government will struggle to control the Taliban, according to AP.

In a February 2020 agreement with the administration of President Donald Trump, the Taliban agreed to halt attacks and hold peace talks with the Afghan government, in exchange for a U.S. commitment to a complete withdrawal by May 2021.

Over the past year, U.S. military commanders and defense officials have said that attacks on U.S. troops have largely paused, but they say the Taliban have increased attacks on the Afghans.

Commanders have argued that the Taliban have failed to meet the conditions of the peace agreement by continuing attacks on the Afghans and failing to totally cut ties with al-Qaida and other extremist groups.

When Biden entered the White House in January, he was keenly aware of the looming deadline and had time to meet it if he had chosen to do so. He began a review of the February 2020 agreement shortly after taking office and has been consulting at length with his defense and military advisers as well as allies.

In recent weeks, it became increasingly clear that he was leaning toward defying the deadline. "It’s going to be hard to meet the May 1 deadline," Biden said in late March. "Just in terms of tactical reasons, it’s hard to get those troops out."

Tellingly, he added, "And if we leave, we’re going to do so in a safe and orderly way."