TOKYO - Japan's Mitsubishi UFJ Financial Group and Morgan Stanley will merge only part of the U.S. firm's Japan brokerage operation with MUFG's, revising their earlier pact, the Nikkei business daily reported on Wednesday.

Morgan Stanley's equities trading and other Japan operations will now remain under the U.S. investment bank's umbrella, as the two firms have changed their earlier plan to merge all of their Japan securities business operations, the newspaper said.

They also plan to delay the integration of their securities operations, now excluding the trading division of Morgan Stanley, to May next year instead of March, the Nikkei said.

The Asahi newspaper said MUFG will now hold a stake of over 40 percent in the Morgan Stanley unit that will keep the U.S. firm's equities trading.

A spokesman at Morgan Stanley Japan declined to comment on the reports, while MUFG could not be reached for comment.

(Reporting by Yumiko Nishitani)