SAO PAULO (Reuters) -Large food retailers, including Tesco, Sainsbury's and Aldi have urged global grain traders to defend Brazil's soy moratorium initiative, a pact designed to protect the Brazilian Amazon from soy-driven deforestation.

In a letter dated Sept. 5 seen by Reuters, the food grocers directly ask the CEOs of ADM, Bunge, Cargill, Louis Dreyfus Company and China's Cofco "to publicly reaffirm the 2008 cut-off date" for banning purchases of soybeans from farmers in the sensitive biome.

"We are writing to you at a critical moment for the future of the Amazon Soy Moratorium, an initiative your companies have championed, protecting the Amazon for nearly two decades...", the letter said, adding Brazil's competition authority CADE decision to suspend the program in August "poses a serious threat to this vital agreement."

The traders did not immediately respond to a Reuters request for comment.

In the letter, retailers said they welcome traders' efforts to appeal the decision, referring to a court order to reinstate the program.

"Even though a temporary injunction was put in place concerning the immediate implementation of the (CADE) order, action is needed to remove any market uncertainty over this time regarding the protections of this vital ecosystem," the letter said.

According to signatories of the letter, if any suspension of the soy moratorium occurs, they expect the grain traders to be prepared "to immediately deploy an interim compliance measure on an individual company basis until a longer-term solution is secured" to protect the Amazon.