Moscow (Reuters) - Russia will back new sanctions against Iran only if the UN atomic watchdog says efforts to clear up questions about Tehran's nuclear program have been exhausted, Foreign Minister Sergei Lavrov was quoted as saying on Wednesday.

Lavrov was speaking to Russian journalists at a meeting of Caspian Sea states when he appeared to set a condition for drawing up a third round of UN Security Council sanctions on Iran sought by the United States. ""A Security Council resolution will be adopted only after the director general (of the International Atomic Energy Agency, or IAEA) reports that the possibility of resolving some of the remaining issues has been exhausted,"" Interfax news agency quoted Lavrov as saying. No additional clarifications were available on his remarks. Russia is a permanent member of the Security Council and could block a third sanctions resolution. The IAEA has said that a lack of full Iranian cooperation with agency inquiries has made it unable to verify the nuclear program is entirely peaceful. ""But I don't think the IAEA would come out loud and say OK we've done our best and there's no way to solve the remaining issues. The IAEA wants to keep communication lines with Iran open,"" a Vienna diplomat familiar with the IAEA inspection mission in Iran said when asked about Lavrov's comments. ""Declaring possibilities exhausted is a political decision. The IAEA is a technical agency.