TOKYO (Reuters) -Japan Post Holdings ( JPHLF ) is planning to sell shares in Japan Post Bank ( JPSTF ) which could total some 600 billion yen ($4.02 billion), two sources familiar with the matter said, in the latest loosening of ties between the businesses.

The postal giant, whose shareholders include the Japanese government, plans to reduce its stake below 50%, said the two sources and a third person familiar with the plan.

That would give Japan Post Bank ( JPSTF ) more freedom to do business as restrictions intended to protect private companies would be relaxed.

The sale comes as corporate governance reforms are accelerating in Japan with "parent-child" listings, where a company controls a listed subsidiary, being scrutinised and companies under pressure to increase free-float share ratios.

The sale could be decided as soon as this week, the sources said. Japan Post Bank ( JPSTF ) is also planning to launch a share buyback, two of the sources said.

The sources declined to be named as the information is not public.

Shares in Japan Post Bank ( JPSTF ) fell 4% following the Reuters report.

Japan Post ( JPHLF ) and Japan Post Bank ( JPSTF ) said they are considering various options from a capital policy perspective, but no decisions have been made.

Japan Post ( JPHLF ), Japan Post Bank ( JPSTF ) and Japan Post Insurance ( JPPIF ) listed in 2015 in what was Japan's largest privatisation in about three decades.

Japan Post ( JPHLF ) cut its exposure to Japan Post Bank ( JPSTF ) in 2023 and currently owns 61.5%. The postal giant has already reduced its shareholding in Japan Post Insurance ( JPPIF ) to 49.8%.

Japan Post Bank's ( JPSTF ) net profit for the nine months to December climbed 17% to 308 billion yen as rising interest rates boosted profits.

($1 = 149.4300 yen)