U.S. retail giant Wal-Mart Stores Inc. and struggling supermarket operator Seiyu Ltd. said Thursday they are forming a capital alliance that will enable the world's largest retailer to stride into Japan.

Wal-Mart will acquire a 6.1 percent stake in Seiyu, the nation's fourth-largest supermarket chain, for 6 billion yen through a third party allocation by the end of May.

Under the agreement, Wal-Mart will have options to raise its stake in Seiyu to 33.4 percent by the end of this year, 50.1 percent by the end of 2005 and 66.7 percent by the end of 2007. The total equity injection would be 260 billion yen, or $2 billion.