US President Biden formally announced his decision to end the 20-year, largely unsuccessful American effort to remake Afghanistan, declaring on Wednesday that he would withdraw the remaining few thousand United States troops in the country by Sept. 11, reported The New York Times.

“It is time to end the forever war,” Mr. Biden said.

Speaking from the Treaty Room in the White House, the American president made the case that the United States had only one real task in the country: ousting Al Qaeda and making sure that the country would never again be the launching pad for a terror attack on the United States, as it was on Sept. 11, 2001.

“War in Afghanistan was never meant to be a multigenerational undertaking,” Mr. Biden said. “We were attacked. We went to war with clear goals. We achieved those objectives.”

Moments after speaking, Mr. Biden traveled to Arlington National Cemetery to visit the graves of service members who lost their lives in Afghanistan. He said the decision to withdraw American troops was “absolutely clear” to him.

Standing in the rain among rows of white headstones, the president said he was “always amazed at, generation after generation, women and men are prepared to give their lives for their country.”

In announcing his decision, the US president made only passing mention of the other objectives that were added to the mission over the years and that came to justify the continued American military presence. That included building a stable democracy, eradicating corruption and the drug trade, assuring an education for girls and opportunity for women, and, in the end, creating leverage to force the Taliban into peace negotiations.

All may have been noble goals, he suggested, but keeping American troops in the country until they were accomplished was a formula for a perpetual presence after the killing of Al Qaeda’s leader, Osama bin Laden.

“We delivered justice to bin Laden a decade ago,” he said. “And we’ve stayed in Afghanistan for a decade since. Since then, our reasons for remaining Afghanistan have become increasingly unclear.”

If Mr. Biden carries through on his vow to remove all American troops permanently based in the country by the 20th anniversary of 9/11, he will have accomplished a goal that his two immediate predecessors, Presidents Barack Obama and Donald J. Trump, embraced but never completed. Yet a clean break will not be easy, and the risks are considerable.

In a series of briefings during which Pentagon officials argued for a continued, modest presence in Afghanistan to collect intelligence and provide support to still-shaky Afghan forces, they warned that the Taliban could attack American troops and their NATO allies on their way out of the country. So Mr. Biden issued a warning, saying “we’re going to defend ourselves and our partners with all the tools at our disposal.’’

White House officials told The New York Times that Mr. Biden had spoken with Mr. Obama about his decision, and the US president said he had also informed former President George W. Bush, who ordered American forces into Afghanistan almost two decades ago. But after noting that he was the fourth president to deal with the question of troops in Afghanistan — two Republicans and two Democrats — Mr. Biden said, “I will not pass this responsibility on to a fifth.”

Mr. Biden is the first US president to have rejected the Pentagon’s recommendations that any withdrawal be “conditions based,’‘ meaning that security would have to be assured on the ground before Americans pulled back. To do otherwise, military officials have long argued, would be to signal to the Taliban to just wait out the Americans — after which, they would face little opposition to taking further control, and perhaps threatening Kabul, the capital.

But some architects of the policy agreed that it was time to go. Douglas Lute, a retired general who ran Afghan policy on the National Security Council for Mr. Bush and then for Mr. Obama, wrote for CNN with Charles A. Kupchan on Wednesday that “those who argue that we need to stay in Afghanistan to thwart attack against the homeland are wrong,” because the terror threat from inside the country “has been dramatically reduced in the last 20 years.”

For the United States, Mr. Biden’s announcement was a humbling moment. The Afghan war was not only the longest in American history, it was one of the costliest — more than $2 trillion. Nearly 2,400 American service members were killed, and more than 20,000 were wounded.

But the US president said the United States would continue fighting terrorists, “not only in Afghanistan, but anywhere they may arise, and they’re in Africa, Europe, the Middle East and elsewhere.”