They agreed that the ministerial-level officials from the two governments will discuss details to conclude the negotiations.
Ishiba and Trump previously spoke on the phone only on Friday last week, prior to the third ministerial-level session.
Speaking to reporters later on Thursday, Ishiba described the day's phone talks as "very meaningful," saying that the two leaders "further deepened mutual understanding."
Ishiba stressed that his government's stance of urging the United States to remove auto, steel, aluminum and other tariffs has not changed.
The Japanese side sees a possibility of reaching an agreement in the tariff negotiations at a possible bilateral summit on the sidelines of the Group of Seven summit in Canada in mid-June.
While reiterating his intention to hold a bilateral summit with Trump at the occasion, Ishiba said, "If necessary, I may visit the United States for talks with Trump beforehand."
Meanwhile, the prime minister declined to comment on Nippon Steel Corp.'s planned acquisition of United States Steel Corp.
[Copyright The Jiji Press, Ltd.]