"I am pleased to announce that an initial group of 11 countries has significantly reduced their volume of crude oil purchases from Iran," she said.
Clinton said Belgium, the Czech Republic, France, Germany, Greece, Italy, Japan, the Netherlands, Poland, Spain and the United Kingdom were the first to join the United States in an effort to isolate Iran economically in an effort to pressure Tehran to abandon an alleged nuclear weapons program.
The European Union has agreed to comply with the sanctions but allowed its members until July 1 to phase out existing contracts with Iranian suppliers.
"The actions taken by these countries were not easy," Clinton said. "They had to rethink their energy needs at a critical time for the world economy and quickly begin to find alternatives to Iranian oil, which many had been reliant on for their energy needs."
Although not an oil importer, Saudi Arabia said this week it would act unilaterally or in cooperation with members of the Organization of Petroleum Exporting Countries to keep oil supplies intact and oil prices stable while the supply from Iran diminishes.