The Russian mission to the UN has received no proposals from Western states concerning new sanctions against Iran, a source in the Russian delegation told RIA Novosti on Thursday.

The U.S. stepped up calls for fresh harsher sanctions against the Islamic Republic after Tehran had begun enriching uranium to 20%. Russia, a veto-wielding Security Council member, had earlier opposed sanctions but said after Iran's move that it might support the initiative.

On Wednesday, diplomats from the U.S., France and the U.K. said they had sent draft proposals on a new Security Council resolution imposing a fourth set of sanctions against the Islamic Republic to the Russian and Chinese delegations at the UN.

"We did not receive anything from anybody," a source in the Russian delegation said.

Another informed source in the UN told RIA Novosti that "work on the resolution on Iran within the framework of the UN Security Council is yet to begin."

Western powers suspect that Iran's nuclear program is aimed at making weapons, while Tehran claims it needs enriched uranium for civilian energy purposes.

Russian President Dmitry Medvedev said on March 1 he did not rule out that Moscow would back sanctions against Iran, but added that if were used, they should be a "balanced" last resort.

Russia's ambassador to the UN, Vitaly Churkin, said early on Wednesday the country's permanent mission to the United Nations had not yet received any orders from the Kremlin on sanctions against Iran.

NEW YORK, March 4 (RIA Novosti)