The letter, dated Jun 11, threw light on briefing with outside lawyers from Walmart, who said that they have been asked to do a global anti-corruption compliance review of its operation in 2011.
The lawyers from the law firms, Akin Gump and Greenberg Traurig, said that the review focused on China, Mexico and Brazil because they run a high risk of corruption. Based on the review, they also recommended that Wal-Mart also look into its operations in South Africa and India.
"We are taking a deep look at our policies and procedures in every country we operate," said Dave Tovar, a Wal-Mart spokesman.
"Wal-Mart's actions to date significantly inhibit our ability to investigate these allegations," stated the letter.
"We are cooperating with the ongoing federal investigations, and as appropriate, will also continue to assist members of Congress and their staffs in understanding our efforts to address FCPA issues," Tovar said in a statement e-mailed to The Associated Press.
"We have already provided committee staff with one briefing and have another briefing scheduled tomorrow."
According to a report in the New York Times, the Mexican unit of Walmart alleged paid a million dollar bribe to gain benefits and speed up its building permits.