A Russian official close to Security Council talks says the latest United Nations sanctions resolution against Iran has been fully agreed on.
British and US officials also say they are confident the UN will approve the sanctions and that a vote will be taken soon, possibly on Wednesday. New sanctions would be the fourth round to be imposed.
President Mahmoud Ahmadinejad of Iran has warned Iran will not agree to talks on its nuclear programme if a new round of UN sanctions are imposed.
He also said a nuclear fuel-swap deal brokered by Turkey and Brazil was an offer that would not be repeated.
Iran - which denies its nuclear programme has military aims - agreed in May to deposit 1200kg of low-enriched uranium with Turkey, in return for reactor fuel.
But Western powers said the agreement was too little too late.