Iran said Sunday that an upcoming visit this week by the head of the U.N.’s atomic watchdog agency to Tehran has nothing to do with a U.S. push to impose so-called “snapback” sanctions on Iran. The Trump administration last week dismissed near-universal opposition to its demand to restore all U.N. sanctions on Iran, declaring that a 30-day countdown for the “snapback” of penalties eased under the 2015 nuclear deal between Tehran and world powers had begun.