Failure to reach a global customs rules deal could have a "considerable impact" on other areas of global trade negotiation, World Trade Organization Director-General Roberto Azevedo said on Monday during a visit to Mexico.

Late last month, India blocked a deal to simplify, standardise and streamline the rules for shipping goods across borders, know as "trade facilitation", after it demanded concessions on agricultural stockpiling.

"If we don't find a solution for this issue, we could see a considerable impact on other areas of world negotiation," Azevedo said in a speech in Mexico City, referring to WTO negotiations.

"I think that we have an opportunity in September to restart talks and see if a bridge is possible," he added.

India insisted that, in exchange for signing the trade facilitation agreement, it must see more progress on a parallel pact giving it more freedom to subsidise and stockpile food grains than is allowed by WTO rules.

Modi government said last week it believed it could convince other members that its need for more freedom on food subsidies was legitimate, and has said it could sign a deal as early as September if its concerns are addressed.