US Secretary of State Hillary "Clinton says 'we are ready for talks but beside that we prepare for paralysing sanctions against Iran'," Rafsanjani said in his Friday prayer sermon carried live on state radio.
"What can they expect of us when such things are said?", the influential cleric said, adding: "They'd better not repeat these comments so the atmosphere existing in Iran today for talks is not ruined."
Clinton said on Wednesday the administration of President Barack Obama is prepared to push for tough sanctions against Iran if the new dialogue fails.
On Wednesday Iran responded favourably to a call from major powers to resume dialogue on its controversial nuclear programme, while reaffirming that it would continue with its activities in the sector.
Western powers fear that Iran's nuclear drive could be a cover for efforts to build an atomic bomb, but Tehran insists it is aimed purely at generating electricity for a growing population.
Permanent UN Security Council members — Britain, China, France, Russia and the United States — plus Germany have sought to persuade Iran to accept a package of political and economic incentives in exchange for an end to uranium enrichment.
Uranium enrichment lies at the centre of fears about Iran's nuclear programme as the process can make both nuclear fuel and the fissile core of an atom bomb.
Iranian President Mahmoud Ahmadinejad said last week he will present a new package for negotiations aimed at resolving the nuclear standoff.
