US Secretary of State John Kerry said the possible introduction of unilateral sanctions against Iran before the end of the negotiations on Tehran's nuclear program would be counterproductive.
"The United States acting unilaterally is not always the best path to take," RIA Novosti cited him.
"We have a number of other serious partners – China, Russia, France, Germany, Great Britain ... So deciding to act unilaterally is not exactly a strategy for success," the diplomat said, calling on Congress to allow the executive branch to negotiate with Iran.
