Iran has hosted the political leader of Afghanistan's Taliban during the past week, offering Tehran's own help as a mediator in peace talks between the insurgents and the Afghan government that have become stalled in Qatar.
Shi'ite Muslim Iran has been a foe of the hardline Sunni Muslim Taliban for decades, but has been openly meeting with Taliban leaders for the past few years as the United States has started negotiating the exit of its troops from Afghanistan.
Washington has accused Iran in the past of providing covert aid to Taliban fighters against U.S. forces.