WASHINGTON — As the U.S. and its NATO allies gradually reduce their commitments in Afghanistan, foreign policy experts cautioned Tuesday there’s still a long way to go before handing the leadership back to the Afghans.

“We are in the midst of a political, economic and security transition that will likely define the future of the country and region for decades for come,” said Alex Thier, assistant to the administrator and director of the Office of Afghanistan and Pakistan Affairs, a division of the U.S. Agency for International Development.

At a Brookings Institution discussion, Thier, along with two other experts in U.S. foreign policy, credited that transition as a significant success so far in the country that has been America’s “intense focus” during the past decade. But they said they also saw severe risks that could undermine the efforts the U.S. has devoted to the region.

Ronald Neumann, U.S. ambassador to Afghanistan from 2005-07, said the presumption that American troops could walk away from the country worry-free after 2014 is “threatening” and “unrealistic,” since the training period for local Afghan government forces was too short.

“You have to leave people in place for at least two to three years,” said Neumann, who visited Afghanistan in May. “We are not winding down the war on terrorism. We are only winding down our part in it.”

Neumann warned that the U.S. will “pay a very serious price” if the administration did not consider Afghanistan’s security and economic conditions carefully.

Besides actively fighting insurgents, NATO forces have other duties in Afghanistan in the coming years, such as strengthening the country’s economy, and establishing transparency and accountability within the local government, the panelists said.

Although NATO has helped the Afghans to develop “more rapidly than any previous decade” historically, Thier said, the effort is not an unqualified success.

“The progress remains fragile due to ongoing insurgency, lack of political settlements, corruption and still-weak society.” Thier said. “We need to ask what is normal for the people of Afghanistan, and how do they see their own future?”