Mitsubishi UFJ Financial Group Inc. (8306.TO) said Wednesday that it will lift its purchase of Morgan Stanley (MS) common stock to $705 million from $600 million, ensuring the U.S. firm's position as an equity-method affiliate.

Noting that its stake will likely be over 20% once the transaction is completed, the Japanese bank said in a statement it now plans to buy 29.37 million shares for $24 apiece.

Mitsubishi also moved its common stock purchase plan to May 22 from May 13.

The move comes after Morgan Stanley on Tuesday filed a prospectus with the U.S. Securities and Exchange Commission to sell 168.4 million common shares to strengthen its capital resources by increasing its Tier 1 common equity.

-By Shawn Schroter, Dow Jones Newswires; 813-6895-7550; shawn.schroter@dowjones.com