OfficeMax Inc (OMX.N) said Wednesday that Chief Financial Officer Bruce Besanko would leave the third-largest U.S. office supply chain next month to take up the same post at supermarket operator Supervalu Inc (SVU.N).

The retailer, which is awaiting regulatory approval for its proposed merger with larger rival Office Depot Inc (ODP.N), named Deb O'Connor, senior vice president, finance and chief accounting officer, as interim CFO effective August 7.

The news comes during the back-to-school season, the most important period of the year for OfficeMax.

"We believe the departure of Mr. Besanko could create some confusion and distraction for OfficeMax at a time when the company is undergoing a planning process for the pending merger with Office Depot and is in the midst of its busiest selling season," Citi analyst Kate McShane wrote in a note to clients.

OfficeMax shares were down 1 percent at $11.58 on the New York Stock Exchange.

In a statement on Wednesday, OfficeMax said Besanko's last day at the company would be August 6. Besanko, who has been CFO since 2009, was also leading the merger integration planning process with Mike Newman, his counterpart at Office Depot.

Effective immediately, Steve Parsons, OfficeMax executive vice president and chief human resources officer, will take over that role in the integration process.