Walmart told the U.S. government privately in January that India’s new investment rules for e-commerce were regressive and had the potential to hurt trade ties, a company document seen by Reuters showed.

The lobbying effort yielded no result at the time — India implemented the new rules from February 1 — but the document underlines the level of concern at Walmart about the rules. Differences over e-commerce regulations have become one of the biggest issues in frayed trade ties between New Delhi and Washington.

“It came as a total surprise ... this is a major change and a regressive policy shift,” Walmart’s Senior Director for Global Government Affairs Sarah Thorn told the Office of the United States Trade Representative (USTR) in an an e-mail on Jan. 7.

Just months earlier, Walmart had invested $16 billion in Indian e-commerce giant Flipkart, its biggest ever acquisition globally.

In a statement to Reuters on Thursday, Walmart said it regularly offers input to the U.S. and Indian governments on policy issues and this was a “past issue and Walmart and Flipkart are looking ahead”.

In the January letter to the USTR, Walmart said it wanted a six-month delay in the implementation of the rules, but that did not happen. Washington did raise concerns about the policy with New Delhi, but India gave a non-committal response, an Indian trade Ministry official told Reuters at the time.