Washington and the Taliban said they would sign the accord on February 29 -- provided a week-long partial truce holds.

The deal would mark a major turning point in the conflict, setting the conditions for a deal that could ultimately pull US troops out after more than 18 years.

"I welcome today's announcement that an understanding has been reached on a significant reduction in violence across Afghanistan," Stoltenberg said in a statement.

"This is a critical test of the Taliban's willingness and ability to reduce violence, and contribute to peace in good faith.

"This could pave the way for negotiations among Afghans, sustainable peace, and ensuring the country is never again a safe haven for terrorists," he added.

NATO has a 16,000-strong mission in Afghanistan to train, support and advise local forces.