Iran Six mediators are discussing the transition from talks to new sanctions in response to Iran's refusal to fold its controversial nuclear program, a senior U.S. diplomat said on Wednesday.

Iran, which is already under three sets of United Nations sanctions for refusing to halt uranium enrichment, recently announced plans to build 10 new uranium enrichment facilities. Western powers suspect it of pursuing an atomic weapons program.

"At present, we are considering the possibility of a transition from dialogue to sanctions because we have always had two parallel ways [to solve this problem]," U.S. Ambassador to Russia John Beyrle said in an interview with Echo Moskvy radio.

"The hope is always there that Iran could finally respond positively on IAEA proposals, but if not, we have to be prepared for something more serious [than talks]," Beryrle said.

The U.S. diplomat also praised the changes in the Russian stance on the Iranian nuclear problem, which have recently moved Moscow closer to Washington's assessment of the potential Iranian threat.

"Tactically, I would say we are closer than ever before," he said, adding that neither Russia nor the United States wanted to see a nuclear arms race in the Middle East.

The Iran Six are Russia, the United States, China, Britain, France and Germany.

The mediators have long been trying to persuade Tehran to halt uranium enrichment not only through sanctions but also in exchange for economic and diplomatic incentives.

Iran Six envoys last met in New York on January 16 but decided against immediate sanctions against Tehran in the hope to find new political and diplomatic solutions to the problem.

Although Russia is seen as having moved closer to the U.S. position, China is still viewed as stalling on any move toward further sanctions.

MOSCOW, January 20 (RIA Novosti)