Convenience store operators FamilyMart Co. and Uny Group Holdings Co. said Thursday they will postpone the planned signing in August of a basic merger agreement and take more time to work out the details of the deal, which was announced in March.

The two companies said there will be no change to their plan to combine operations in September 2016, a merger that would create Japan's second-largest convenience store operator after Seven-Eleven Japan Co. in terms of sales.

"We judged that it is necessary to continue talks toward a business merger," the companies said in a statement.

It is taking more time than previously expected to decide on how to revive Uny's supermarket store operations, company officials said. A top Uny official dismissed fears that the merger talks could break down.

FamilyMart ranks third in terms of sales in Japan, followed by Uny, operator of Circle K Sunkus convenience stores.

The planned merger is expected to help them streamline business operations such as procurement and join forces to develop new items, industry observers said.

As of the end of July, the combined number of stores operated by FamilyMart and Uny stood at 17,778 in Japan, compared with the 17,886 operated by Seven-Eleven Japan.

FamilyMart also said it has decided to liquidate its U.S. convenience store subsidiary Famima Corp. to devote resources to Asia, where the Japanese company sees high growth potential.

Based in California, Famima was founded in October 2004 and had eight stores as of the end of July.