President Joe Biden says the Sept. 11 attacks “cannot explain” why U.S. forces should remain in Afghanistan 20 years later and that “it is time for American troops to come home” from the country's longest war.

Bidensays the U.S. cannot continue to pour resources into an intractable war and expect different results. The White House released the excerpts before the afternoon address when he plans to detail his timeline for a U.S. troop withdrawal.

“We cannot continue the cycle of extending or expanding our military presence in Afghanistan hoping to create the ideal conditions for our withdrawal, expecting a different result,” Biden says. “I am now the fourth American president to preside over an American troop presence in Afghanistan. Two Republicans. Two Democrats. I will not pass this responsibility to a fifth.”

Biden says he consulted with allies, military leaders, lawmakers and Vice President Kamala Harris to help make his decision to withdraw all U.S. troops by Sept. 11, two decades after the deadliest attack on American soil.

He is emphasizing that his administration will continue to support peace talks between the Afghan government and the Taliban and assist international efforts to train the Afghan military.

“It is time to end America’s longest war,” Biden says. “It is time for American troops to come home.”

All U.S. troops from Afghanistan will be withdrawn by by Sept. 11, the 20th anniversary of the terrorist attacks on America that were coordinated from that country, several U.S. officials said.

Biden will lay out his vision for the way forward in Afghanistan and the timeline for the withdrawal in remarks Wednesday afternoon, The White House said. Punctuating the nearly two decades U.S. troops have fought and died in Afghanistan, the president will then visit Section 60 of Arlington National Cemetery to honor the sacrifice of those who died in recent American conflicts.

The decision to withdraw troops by fall defies a May 1 deadline for full withdrawal under a peace agreement the Trump administration reached with the Taliban last year, but leaves no room for additional extensions. A senior administration official on Tuesday called the September date an absolute deadline that won't be affected by security conditions in the country.

While Biden's decision keeps U.S. troops in Afghanistan four months longer than initially planned, it sets a firm end to two decades of war that killed more than 2,200 U.S. troops, wounded 20,000, and cost as much as $1 trillion. The conflict largely crippled al-Qaida and led to the death of Osama bin Laden, the architect of the Sept. 11 attacks. But an American withdrawal also risks many of the gains made in democracy, women's rights and governance, while ensuring that the Taliban, who provided al-Qaida's haven, remain strong and in control of large swaths of the country.

Biden has been hinting for weeks that he was going to let the May deadline lapse, and as the days went by it became clear that an orderly withdrawal of the roughly 2,500 remaining troops would be difficult and was unlikely. The administration official said the drawdown would begin by May 1.

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-Qaida from establishing a foothold again that could be used to launch attacks against the U.S.

The administration official said Biden decided that the withdrawal deadline had to be absolute, rather than based on conditions on the ground. “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.”

Defense officials and commanders had argued against the May 1 deadline, saying the U.S. troop withdrawal should be based on security conditions in Afghanistan, including Taliban attacks and violence.

White House press secretary Jen Psaki didn't provide details of Biden's remarks planned for Wednesday, but she said during a White House briefing that Biden "has been consistent in his view that there is not a military solution to Afghanistan, that we have been there for far too long.”

Psaki tweeted later Tuesday that Biden's visit to Arlington National Cemetery was “to pay his respects to the brave men and women who have paid the ultimate sacrifice in Afghanistan.”

Several U.S. officials confirmed Biden’s withdrawal decision to The Associated Press, and an administration official provided details to reporters on condition of anonymity, speaking ahead of the announcement.

According to the administration official, the only U.S. forces remaining in Afghanistan will be those needed to protect diplomats there. No exact number was provided, but American troop totals in Afghanistan have been understated by U.S. administrations for years. Officials have quietly acknowledged that there are hundreds more in Afghanistan than the official 2,500 number, and likely would include special operations forces conducting covert or counterterrorism missions, often working with intelligence agency personnel.

Biden's new, extended timeline will allow a safe and orderly withdrawal of American troops in coordination with NATO allies, the administration official added.

The president's decision, however, risks retaliation by the Taliban on U.S. 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.

Congressional reaction to the new deadline was mixed.

“Precipitously withdrawing U.S. forces from Afghanistan is a grave mistake," said Senate Republican leader Mitch McConnell, R-Ky. “It is retreat in the face of an enemy that has not yet been vanquished and abdication of American leadership.”

Sen. Jim Inhofe of Oklahoma, the ranking Republican on the Senate Armed Services Committee, slammed it as a “reckless and dangerous decision.” He said any withdrawal should be conditions-based, adding that arbitrary deadlines could put troops in danger, create a breeding ground for terrorists and lead to civil war in Afghanistan.

Democrats were generally more supportive. Sen. Jack Reed, D-R.I., chairman of the Armed Services Committee, said President Donald Trump’s May 1 deadline limited Biden’s options. “We still have vital interests in protecting against terrorist attacks that could be emanating from that part of the world, but there are other areas, too, we have to be conscious of,” Reed said.

Sen. Tim Kaine, D-Va., said troops should come home, and the U.S. must refocus American national security on more pressing challenges.