Sept. 25 (Bloomberg) -- UnionBanCal Corp., the San Francisco-based lender sold to Mitsubishi UFJ Financial Group Inc. last year, said its new parent will invest $2 billion to brace the company against loan losses.

The injection, which UnionBanCal called “voluntary and pre- emptive,” was based on scenarios used for U.S. stress tests of the nation’s biggest banks that were more pessimistic than the bank actually expects, Chief Executive Officer Masaaki Tanaka said today in a statement.

“To the extent actual credit costs are consistent with, or lower than, those in our base forecast, we will have considerable excess capital that could be deployed to support incremental organic growth and acquisitions,” Tanaka said.

Mitsubishi, Japan’s biggest bank by market value, paid about $3.6 billion last year for shares of UnionBanCal that the Tokyo-based company didn’t already own. The California lender had shunned subprime lending and dodged the worst of the U.S. housing market’s collapse through the middle of 2008.

Union Bank, the commercial banking subsidiary, has $73.6 billion in assets and $59 billion in deposits at 339 branches concentrated in California, Washington and Oregon, according to Federal Deposit Insurance Corp. data. The investment will increase tangible common equity at the lender by 43 percent to $6.7 billion, according to the statement.

Union Bank is the 22nd-largest bank and thrift by assets in the U.S., and the third-largest bank based in California, according to SNL Financial LLC, the bank research firm in Charlottesville, Virginia.

To contact the reporter on this story: Dakin Campbell in New York at dcampbell27@bloomberg.net

Last Updated: September 25, 2009 14:47 EDT