U.S. Vice President Joe Biden has rejected calls for more sanctions against Iran over its nuclear program, saying "this is not the time to risk a breakdown when we still have a chance for a breakthrough."
Biden, speaking at a forum at the Brookings Institution in Washington, said the sanctions already imposed on Iran were working by slowing the country's economy, as well as its nuclear program.
"It's given us a shot for a peaceful solution," he said.
Iran and six powers failed last month to resolve a 12-year stand-off over Tehran's nuclear ambitions, and gave themselves seven more months to clinch an historic deal.
Britain, China, France, Germany, Russia, and the United States want to curb Iran's uranium enrichment to lengthen the time it would need to build a bomb.
Iran denies it is seeking to develop a nuclear weapons capability.