"Japan has consistently upheld the nuclear agreement and believes it is important for all sides to adhere to its provisions," Kono was quoted as saying Thursday by the NHK broadcaster.
Speaking after a meeting in Belgium with his Iranian counterpart, Mohammad Javad Zarif, Taro Kono said their countries had agreed that the United States should not exit the pact, and promised support to Tehran.
Trump has repeatedly criticized the 2015 nuclear pact which limited Tehran’s nuclear research in return for sanctions easing. In January, Trump asked Congress to address "flaws" in it. The United States is expected to announce whether it will extend sanctions waivers for Iran on May 12.