Wal-Mart Stores Inc (WMT.N) and American Express (AXP.N) will hold a conference call on Monday to make a financial services announcement, the two companies said in a statement on Sunday.

Details of the announcement, which will take place at 8:30 a.m. EST, were not disclosed.

Walmart, the world's largest retailer, has long tried to serve the large group of its low-income shoppers who have little or no access to credit. The retailer offers check cashing at low rates and other services as it tries to appeal to shoppers without bank accounts.

Walmart has said in the past that about 85 percent of transactions at its U.S. stores are paid for with cash.