Japanese Prime Minister Shinzo Abe (L) and U.S. President Donald Trump meet the press in Biarritz, southwestern France, on Aug. 25, 2019, as they hold bilateral talks on the sidelines of a Group of Seven summit. (Kyodo) 

TOKYO - U.S. President Donald Trump last year urged Prime Minister Shinzo Abe to act as a mediator between the United States and Iran amid heightened tensions between Washington and Tehran, even though he did not expect the Japanese leader to succeed in the mission, former U.S. National Security Adviser John Bolton said in his memoir published Tuesday.