The UN Security Council is due to vote in New York on whether to impose further sanctions against Iran.
Iran insists its nuclear programme is purely peaceful in purpose
The move was announced by Britain's UN envoy, who predicted a unanimous vote.
The sanctions would block Iranian arms exports and freeze the assets of individuals and companies involved in Iran's nuclear and missile programmes.
President Mahmoud Ahmadinejad will not be present because the US delayed issuing visas, Iranian officials say. The US has denied the claims.
The vote is scheduled at 1500 (1900 GMT) on Saturday unless there are any last minute changes when the text is sent to governments of the 15 council members for final approval.
"There will be a vote tomorrow and we are all determined that vote will be unanimous," Britain's UN ambassador, Emyr Jones Parry, told reporters on Friday.
After last-minute negotiations, objections from South Africa, Qatar and Indonesia to the text drafted by the five permanent UN Security Council members and Germany seem to have been overcome, The BBC's Laura Trevelyan at the UN says.
'Excuse not to go'
The Iranian leader had wanted to address the Security Council before it holds any vote on further sanctions against Tehran for refusing to suspend uranium enrichment.
In December, the Security Council imposed limited sanctions on the country over its refusal to halt the programme, which Iran insists is purely peaceful in purpose.
Mr Ahmadinejad said he wanted to address the Security Council
The sanctions, agreed on last week by the six powers, would block Iranian arms exports and freeze the assets of individuals and companies involved in Iran's nuclear and missile programmes.
The Iranian spokesman told the BBC that instead of the president, Iran's foreign minister and his deputy hoped to attend, travelling on a commercial flight.
Iranian spokesmen blame the US for delaying issuing visas to the air crew. The US say the visas were issued and the Iranian leader is looking for an excuse not to come.