TOKYO (Reuters) - Japan Post Holdings Co (>> Japan Post Holdings Co Ltd) CEO Taizo Nishimuro is set to resign in coming weeks, two people with direct knowledge of the matter said on Friday, amid speculation over his health following his hospitalization nearly a month ago. The company has started a search for his successor, with potential candidates including top managers from other companies, said the sources, who were not authorized to discuss the matter publicly.

Japan Post representatives could not immediately be reached for comment.

If the search for a successor is prolonged, the resignation could be delayed the sources said. Nishimuro's renewable term expires in June, but he has previously expressed a desire to remain until well into next year.

The 80-year-old former president of Toshiba Corp (>> Toshiba Corp) and the Tokyo Stock Exchange has been hospitalized since Feb. 8 for what Japan Post has said were unspecified tests.

Nishimuro took the helm at Japan Post in 2013, orchestrating the world's biggest public offering last year - the $12 billion sale in November of shares in the parent company, which controls the nation's mail-delivery service, and its two financial units, Japan Post Bank Co (>> Japan Post Bank Co Ltd) and Japan Post Insurance Co (>> Japan Post Insurance Co Ltd).

He told reporters in November there were no clear plans for a successor.

"As for myself, I would like from the bottom of my heart to do two annual shareholders meetings and around then decide on my successor" around June or July 2017, Nishimuro said.

($1 = 113.7100 yen)

(Reporting by Takaya Yamaguchi; Writing by Taiga Uranaka; Editing by William Mallard and David Evans)

By Takaya Yamaguchi