Prime Minister Shinzo Abe, who has unexpectedly announced his resignation, plans to hold phone talks with U.S. President Donald Trump on Monday, Japanese and U.S. government sources said Saturday.

Abe, who said Friday he will step down from the post he has held since 2012, is expected to tell Trump he had to resign before the end of his term to undergo prolonged treatment for his ulcerative colitis, a chronic illness.

The sudden resignation announcement came just a few days after Abe achieved the longest uninterrupted stint as prime minister in Japanese history. Since the announcement, the race to find Abe's successor has been intensifying.