TOKYO (Reuters) - Mitsubishi Motors ( MMTOF ), a junior partner of Nissan Motor ( NSANF ), is considering not joining a planned business merger between Nissan ( NSANF ) and Honda Motor ( HMC ), the Yomiuri online said on Friday.

The report came after Nissan ( NSANF ) and Honda ( HMC ) last year said they would begin formal talks on the merger that could potentially create the world's third-largest auto group.

Mitsubishi Motors ( MMTOF ), in which Nissan ( NSANF ) is the top shareholder with a 24% stake, was expected to decide by this month whether it plans to take part.