South Africa's antitrust watchdog Friday extended its review of the proposed $2.4 billion takeover of local retailer Massmart Holdings Ltd. (MSM.JO) by Wal-Mart Stores Inc. (WMT) by 15 days.

The move was in response to an application to the Competition Commission for additional time to submit evidence from labor unions opposed to the deal. Massmart said it and Wal-Mart opposed the application, arguing that unions would have an opportunity to present evidence during public hearings to be held by the Competition Tribunal.

"Massmart understands that it is important for all stakeholders to be afforded sufficient opportunity to present their concerns in good faith," said Grant Pattison, chief executive of Massmart. "We therefore respect the Competition Tribunal's subsequent decision to grant a 15-day extension in order to accommodate the union."

Massmart's shareholders last week voted in favor of the Bentonville, Ark.-based retail giant's offer to buy a 51% stake at 148 rand ($20.93) a share. Pattison at the time said he expected the Competition Commission to make its recommendations on the tie-up this month.

The South African Commercial, Catering and Allied Workers Union in a statement welcomed the decision. "We believe this decision is significant and sends a clear signal to business that they should not assume, as Mr. Grant Pattison did, that the Commission is there to serve the interests of business only," it said.

The union said the commission should consider the possible affect on the retail and wholesale industry, as well as on the local supply base, of a deal between the two companies. It has accused Wal-Mart of being antiunion.

Wal-Mart has repeatedly said it would honor all existing agreements with unions and local labor laws if the deal goes ahead. The agreement proposes that Massmart remain listed in Johannesburg, and both companies have said the existing management team will stay in place.

Massmart operates several wholesale and retail chains, including Game general-merchandise stores, Builders Warehouse for construction and Makro warehouse-club stores. The bulk of the company's 288 stores are in South Africa, although it also operates in 13 other sub-Saharan countries.

-By Robb M. Stewart, Dow Jones Newswires; +27 11 783 7848; robb.stewart@dowjones.com