Mounting pressure by Iran's hardliners behind Zarif's resignation - ally

DUBAI (Reuters) - Political infighting in Iran after Washington last year quit a nuclear deal between Iran and world powers forced Foreign Minister Mohammad Javad Zarif to announce his resignation, a close ally told Reuters on Tuesday.

"Zarif and President (Hassan) Rouhani have been under a huge amount of pressure from top officials since last May ... the U.S. exit intensified political infighting in Iran," said Zarif's ally, who asked not to be named.

(Writing by Parisa Hafezi; Editing by Kevin Liffey)