Bank of America Corp. Chief Executive Kenneth Lewis pledged on Thursday to complete the $21 billion acquisition of all of LaSalle Bank from ABN AMRO Holding NV early in the fourth quarter.

Lewis tried to reduce speculation that the second-largest U.S. bank might keep LaSalle's Chicago-area business, which includes many affluent clients, while selling its Michigan-based business, where the area economy is weaker.

We expect to have the entire company, and are looking forward to having it, Lewis said on a conference call discussing second-quarter results. We like it as it is. We think it has a great (internal rate of return), and some upside potential as well.

The transaction would give Bank of America control of about 10 percent of U.S. deposits, the maximum allowed under federal limits.

(Reporting by Jonathan Stempel)