Qatar PM to visit Tehran to pursue mediation efforts

By Yomna Ehab and Parisa Hafezi CAIRO/DUBAI, Aug 27 (Reuters) - Qatar's prime minister will visit Tehran on Thursday in an effort to relaunch diplomacy after the U.S. and Iran traded recriminations over Washington's promise to increase economic pressure on Tehran by targeting its trade partners for sanctions. Qatar, a Gulf neighbour of Iran and a U.S. ally, has served as a back-channel negotiator for the warring parties and played a direct role in securing the June ceasefire that briefly led to…