Russia could agree to sanctions against Iran if the Islamic Republic fails to answer proposals for resolving the current nuclear crisis, Foreign Minister Sergei Lavrov said, in an apparent hardening of his country's position.

"If the first resolution calling on Iran to respond to the demands of the IAEA doesn't work, we have agreed that after a period it will be necessary to discuss additional measures, including measures of an economic character," Lavrov told Echo Moscow radio in an interview on Wednesday.

"This period should be a reasonable one so that Iran can realise the attractiveness of the proposals.

"The resolution currently being discussed… says that the (UN) Security Council, while expecting an answer from Iran, intends to look at additional measures if there isn't an answer. It clearly states that these measures do not include the use of force," Lavrov said.

"If after a certain period we don't hear an answer from Iran and discussions aren't renewed, we will look in the Security Council at additional measures," he said.

The proposals put to Iran were presented by the five permanent members of the United Nations Security Council plus Germany in June. They offer trade, political and economic incentives.

The lack of response from Iran has led to renewed discussion of the issue in the Security Council.

The United States has led calls for Iran to suspend sensitive nuclear fuel cycle work, suspecting that Tehran's stated desire for peaceful nuclear energy is a cover for a weapons programme.

Russia is a close ally of Iran and is building the Islamic Republic's first nuclear power station at Bushehr, a project the US has said should be halted.