NATO chief Jens Stoltenberg says the transatlantic alliance will decide the fate of its training mission in Afghanistan at its next defense ministers' meeting, in February.
"We will be faced with a difficult choice," Stoltenberg told the audience at a NATO event on November 23, according to a transcript quoted by the dpa news agency.
"Either stay -- and pay the price of a continued military engagement. Or leave -- and risk that the gains we have made are lost. And that the peace process falters."
His remarks follow last week's announcement by the outgoing administration in Washington that the United States would cut its troop numbers in Afghanistan from its current figure of 4,500 to around 2,500.
"The NATO mission will remain," Stoltenberg said at the time in response to the reduction ordered by U.S. President Donald Trump. "And we will continue to provide support to Afghan security forces."
Trump, who came to office on "only America first" pledges and vows to extricate the United States from "endless wars," also announced a similar troop cut in Iraq.
Washington led an international invasion of Afghanistan after the 9/11 terror attacks against the United States in 2001 to track down and punish Osama bin Laden and his Al-Qaeda terror group that was based there.
But extricating itself from the conflict while safeguarding against international terrorists establishing a new haven there has proved difficult.
U.S. troops continue to provide crucial support to the Afghan central government as it tries to combat threats from Taliban and other Islamist militants who routinely target security forces and civilians in an ongoing battle for control of territory and influence.
In blunt public remarks, Stoltenberg last week warned against precipitous foreign troop cuts in Afghanistan.
The country could again become a base for international terrorist groups that target the West, he said.
The prospects of fundamentalist Taliban militants gaining power in Kabul -- either as part of a possible peace deal or seizing control following an international withdrawal -- have raised concerns that small but significant gains in human rights and girls' education over the past two decades could be reversed.
UN High Commissioner for Refugees Filippo Grandi warned at the opening of a donors' conference on Afghanistan in Geneva on November 23 that the global community risks "disastrous consequences" if it abandons aid to that country.
During a visit to Qatar, where tough peace talks between the Afghan government and the Taliban opened in September, U.S. Secretary of State Mike Pompeo on November 21 called on the militant group's leaders to swiftly negotiate a permanent cease-fire in Afghanistan.
A State Department spokesman said Pompeo "called for a significant reduction in violence and encouraged expedited discussions on a political road map and a permanent and comprehensive cease-fire."