High-wire diplomacy delivered US-Iran deal but hardest stage lies ahead, sources say

By Saad Sayeed, Andrew Mills, Ariba Shahid and Olivia Le PoidevinISLAMABAD, June 18 (Reuters) - Pakistani mediators spent weeks juggling late-night calls and competing drafts before a Qatari push helped secure this week's preliminary U.S.-Iran deal, but turning it into a permanent agreement will prove harder, sources said.