Updated

A senior Russian diplomat has rejected U.S. warnings against striking an oil-for-goods contract with Iran.

Deputy Foreign Minister Sergey Ryabkov said Wednesday in remarks carried by the RIA Novosti news agency that an increase in Russian-Iranian trade is a "natural process that doesn't involve any elements of political or economic challenge to anyone."

Russian business daily Kommersant has reported that Moscow plans to buy 500,000 barrels of Iranian oil a day, a deal that would shatter an export limit defined by an interim nuclear agreement world powers and Iran reached last year.

Ryabkov said he was unaware of any specific agreements, adding that a "normal exchange of opinions with Iranian colleagues has been going on to determine which sectors of economy are best suited for further development of ties."