WASHINGTON, September 28 (RIA Novosti) - U.S. State Secretary Hillary Clinton has praised Russia's willingness to cooperate with the West on taking a tougher stand on Iran and N. Korea over their nuclear ambitions.

Speaking on CBS "Face the Nation" program aired on Sunday, Clinton "repeatedly brought up Russia and President Medvedev, who spoke in support of sanctions against Iran Friday, after being informed by President Obama this week about the existence of the previously-secret nuclear facility."

"We believe in working closely with Russia, sharing information, that they have been quite helpful this past week," Clinton said, adding that the recent shift in Russia's position clearly demonstrated the power of diplomacy and cooperation.

Russia, which has traditionally supported Iran in the long-running dispute over its nuclear program, voiced concern on Friday over the second enrichment site, and urged the country to provide reassurances over its nuclear program.

President Dmitry Medvedev said in a statement circulated at a G20 economic summit in Pittsburgh that the fact that Iran has been building a uranium facility for several years without informing the UN nuclear watchdog is a "source of serious concern."

He urged the country to take steps to prove that its nuclear program is peaceful before a meeting with six world powers in Geneva on October 1.

Iran has been under international pressure to halt uranium enrichment, used in both electricity generation and weapons production. Tehran has repeatedly rejected the demand, insisting it is pursuing a purely civilian program. Several Western powers have called for harsher sanctions against Tehran if it does not agree to halt uranium enrichment.

The U.S. State Secretary also said Russia had expressed significant support of U.S.-proposed sanctions against N. Korea.