Sushi restaurant chains Akindo Sushiro Co. and Genki Sushi Co. are in merger talks to speed up the expansion of their overseas business, the companies said Friday.

Akindo Sushiro operates Japan's largest conveyor belt sushi chain with around 470 restaurants, most of them domestic. Genki Sushi, the No. 5 chain, runs more than half of its 300 or so restaurants abroad, including in the United States and China.

By teaming up, they hope to cut down on costs and pool their resources to open more restaurants across the growing Asian market, especially as Japan's graying population puts a damper on domestic sales.

In preparation for the merger, Shinmei Co., the parent company of Genki Sushi and Japan's largest rice wholesaler, plans to acquire a 32.72 percent stake in Sushiro Global Holdings Ltd., parent of Akindo Sushiro.

While the details of the merger are still being worked out, combining the two businesses would give the new company a significant lead in revenue over its closest rival, Kura Corp.