NATO says it will pull out all its troops from Afghanistan, matching a U.S. pledge to do the same.
NATO chief Jens Stoltenberg, after meeting Wednesday with U.S. Secretary of State Anthony Blinken and Secretary of Defense Lloyd Austin, announced at a news conference that about 7,000 NATO troops would be withdrawn.
"We will start the withdrawal of NATO Resolute Support forces by May 1," Stoltenberg said. "We plan to complete the withdrawal of all our troops within a few months.
"We went into Afghanistan together, we have adjusted our posture together and we are united in leaving together," he said, adding that any attacks on withdrawing NATO forces would draw a firm and forceful response from the alliance.
The U.S. and NATO said troop withdrawal was not an abandonment of Afghanistan.
"Bringing our troops home does not mean ending our relationship with Afghanistan or our support for the country," Blinken said. "Our support, our engagement and our determination remain."
The Biden administration ended months of speculation about U.S. plans in Afghanistan by saying Tuesday that it would withdraw remaining troops by September 11, the 20th anniversary of the 2001 attacks in which al-Qaida terrorists hijacked passenger planes and crashed them into the World Trade Center in New York and the Pentagon in Washington.
That same day, another domestic passenger flight, United Airlines Flight 93, was hijacked by four al-Qaida terrorists and crashed in a field in Somerset County, Pennsylvania.
The attacks prompted the United States to topple the Taliban in Afghanistan in an effort that eventually grew to include more than 130,000 troops from 50 NATO and partner nations. Since 2015, the remaining forces, which now number fewer than 10,000, have been tasked with training and assisting Afghan security forces.
U.S. officials had said the decision to leave Afghanistan would be taken in conjunction with NATO allies.
Wednesday's discussions focused on the Russia-Ukraine border, where Russia has been amassing its forces.
Stoltenberg called Russia's actions "aggressive" and said it must "stop provocations and deescalate."
Blinken said during his first day in Brussels on Tuesday that the United States "stands firmly behind the sovereignty and the territorial integrity of Ukraine."
The White House said President Joe Biden also "emphasized the United States' unwavering commitment to Ukraine's sovereignty and territorial integrity" during a phone call Tuesday with Russian President Vladimir Putin.
"The president voiced our concerns over the sudden Russian military buildup in occupied Crimea and on Ukraine's borders, and called on Russia to deescalate tensions," the White House said in a readout of the conversation, adding that Biden "proposed a summit meeting in a third country in the coming months to discuss the full range of issues facing the United States and Russia."
The Kremlin is overseeing the largest movement of Russian troops, tanks and missiles along the Ukrainian border since the annexation of Ukraine's Crimean Peninsula in 2014, according to Ukrainian and U.S. officials. Russia has conducted at least three military training exercises adjacent to the Ukrainian border since mid-March.
Ukrainian Foreign Minister Dmytro Kuleba expressed confidence Tuesday that Western countries would also act to temper Russian aggression, which he said would force Ukraine to pay too high a price if left unchecked.
Two U.S. warships are set to arrive in the Black Sea this week amid an escalation in fighting in eastern Ukraine between Ukrainian forces and Russian-backed troops.
The conflict over Crimea has left about about 14,000 people dead, according to Ukraine's government.
Kuleba said Ukraine "does not want war" and is "devoted to diplomatic and political means of settling the conflict."
But while highlighting support for NATO, Kuleba also said: "Should Russia take any reckless move or start a new spiral of violence, it will be costly in all senses."