The US unilaterally pulled out of the 2015 nuclear deal last year. It recently banned all countries from importing Iranian crude oil and dispatched a carrier strike group and B-52 bombers to the Middle East.
Iranian President Hassan Rouhani said last week that his country would restart part of its nuclear activity if Iran’s interests are not protected against US sanctions.
Zarif visited Russia and India before travelling to Japan.
He has been explaining that the US hardline stance has forced Iran to take countermeasures.
Zarif is also expected to seek Japan’s cooperation as it plans to hold negotiations with European nations in an effort to keep the nuclear deal alive. Japan has consistently supported the agreement.
Zarif may also ask Japan to maintain trade with Iran where possible, despite the tightening of US economic sanctions.