President Joe Biden will withdraw all troops from Afghanistan by September 11, the 20th anniversary of the terrorist attacks on America that were coordinated from the Asian country, US officials said.

The decision defies a May 1 deadline for full withdrawal under a peace agreement the Trump administration reached with the Taliban last year.

But Mr 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 on 1.

Mr Biden’s choice of the 9/11 date underscores the reason that American troops were in Afghanistan to begin with — to prevent extremist groups like al-Qaeda from establishing a foothold again that could be used to launch attacks against the US.

Afghan children carry containers of water at Gul Ghundi park in the city of Charikar in Parwan province, north of Kabul, Afghanistan
Afghan children carry containers of water at Gul Ghundi park in the city of Charikar in Parwan province, north of Kabul (Rahmat Gul/AP)

The president decided that the deadline for withdrawal of US forces had to be absolute, rather than provisional on conditions inside Afghanistan as the deadline neared, the senior administration official said.

“We’re committing today to going to zero” US forces by September 11, and possibly well before, the official said, adding that Mr Biden concluded that a conditioned withdrawal would be “a recipe for staying in Afghanistan forever”.

US officials provided details on Mr Biden’s decision on condition of anonymity, speaking ahead of the announcement. It was first reported by The Washington Post.

According to the administration official, the only US forces remaining in Afghanistan will be those deemed necessary to protect diplomats in the country. An exact number had yet to be decided.

The extended timeline will allow a safe and orderly withdrawal of American troops in coordination with Nato allies, the administration official added.

Mr Biden’s decision risks retaliation by the Taliban on US and Afghan forces, possibly escalating the 20-year war. And it will reignite political division over America’s involvement in what many have called the endless war.

An 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.

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 US commitment to a complete withdrawal by May 2021.

Over the past year, US military commanders and defence officials have said that attacks on US 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-Qaeda and other extremist groups.

When Mr 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 defence 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,” Mr 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.”