Japan premier hopes to ease US-Iran tensions in Tehran visit

Japanese Prime Minister Shinzo Abe' s trip to Tehran represents the highest-level effort yet to de-escalate tensions between the U.S. and Iran as the country appears poised to break the 2015 nuclear deal it struck with world powers that America earlier abandoned.

But while Abe' s trip to Iran marks the first visit of a sitting Japanese premier i n the 40 years since the Islamic Revolution, it remains unclear if he'll end up going home with any success.

Iran is threatening to resume enriching uranium closer to weapons-grade level on July 7 if European allies fail to offer it new terms.