Struggling U.S. financial giant Citigroup Inc. is testing local interest in Nikko Asset Management Co., a key Japanese unit it wants to sell for roughly ¥100 billion, sources familiar with the matter said Saturday.

While Japan's megabanks and some life insurers have shown an interest in the unit, Mitsubishi UFJ Financial Group Inc., the largest of the megabanks, is seen as the front-runner, the sources said.

The group's core member, Mitsubishi UFJ Trust and Banking Corp., announced a plan in December to buy NikkoCiti Trust and Banking Corp., another local Citigroup unit, for ¥25 billion.

Nikko Asset was founded in 1959 mainly to manage investment trusts. In recent years, it has been aiming to go public under Citi's wing.