Moscow: Russia on Friday rejected any talk for now of sanctions against Iran and France warned against conflict with Tehran, raising doubt whether it will face swift penalties for not halting nuclear work by an August 31 deadline.

Responding to an offer of economic incentives to stop enriching uranium, Iran hinted to six world powers on Tuesday it could curb its programme as a result of talks to implement the package, but not as a precondition as they demand.

The reply seemed designed to crack the ramshackle united front of four Western powers and Russia and China behind the Security Council deadline. The West sees Iran's nuclear work as a threat to peace. Russia and China do not.

"I know of no instances in world practice and previous experience in which sanctions have achieved their aim and proved effective," Russian Defence Minister Sergei Ivanov told reporters during a trip to Russia's far east.

"Moreover, I believe that the question is not so serious at the moment for the UN Security Council or the group of six to consider any introduction of sanctions. Russia stands for further political and diplomatic efforts to settle the issue."

European Union foreign policy chief Javier Solana said on Friday that Tehran's reply had touched on "many different elements, different from the ones that we had proposed".

"For that reason we will have to hold a dialogue session ... or a conversation with the ... Iranians to improve upon some of the expressions and meanings of the subject matter treated in its document," he told Spain's RNE state radio.

But while Washington, backed by closest ally Britain, has said the six powers will move quickly to adopt sanctions if Iran disregards the deadline, Germany and France have been less conclusive in public and Russia and China have been unwilling.

"For the moment, it [the Iranian response] is not satisfactory," French Foreign Minister Philippe Douste-Blazy said, but added it was important to avoid escalating conflict with Iran and the Muslim world.

"The worst thing would be to escalate into a confrontation [between the West and] Iran on the one hand, and the Muslim world with Iran," he said.

"I'm starting from the principle we should have a dialogue with the Iranians, that we must hold out our hands to them."