Mahmoud AhmadinejadPresident Mahmoud Ahmadinejad has warned Iran will not agree to talks on its nuclear programme if a fourth round of UN sanctions are imposed this week.
He also said a nuclear fuel-swap deal brokered by Turkey and Brazil was an offer that would not be repeated.
Mr Ahmadinejad urged Russia not to side with Iran's enemies and said the US would lose if new measures were passed.
The sanctions would tighten financial curbs and shipping inspections on Iran, and expand a limited arms embargo.
Diplomats expect the vote to happen as early as Wednesday and there is little doubt the resolution will be adopted, says the BBC's Barbara Plett, at the UN.
At a news conference in Istanbul on Tuesday, where he has been attending a regional security summit, Mr Ahmadinejad urged President Barack Obama to reconsider.
"I'm not saying I'm totally disappointed but if he fails to make a change, the first ones to lose would be President Obama and the people of the United States," he was quoted as saying by Reuters news agency.
Mr Ahmadinejad also urged Russia to be "careful not to be beside the enemies of the Iranian people".
Although Moscow has often cautioned against tough action on Iran, it is backing the current draft UN resolution.
Mr Ahmadinejad is expected to hold talks later on Tuesday with Russian Prime Minister Vladimir Putin, who is also attending the summit in Turkey.
The Iranian leader added: "I have said that if the American government and its allies think that they can raise a baton called a resolution and then sit and talk to us, they are strongly mistaken."
Israel criticismMr Ahmadinejad will travel to China on Friday and visit the World Expo in Shanghai, Beijing's foreign ministry said, but it is not clear if he will hold any talks with Chinese leaders.
The BBC's Jonathan Head in Istanbul says Mr Ahmadinejad reserved particular criticism for Israel.
Labelling it a "fake, Zionist regime", he said it had started the "countdown to its destruction" through its attack last week on a Gaza-bound aid flotilla.
Iran - which denies its nuclear programme has military aims - agreed in May to deposit 1,200kg of low-enriched uranium with Turkey, in return for reactor fuel.
But Western powers said the agreement was too little too late.
The draft resolution includes the following proposals:
- Prohibiting Iran from buying several categories of heavy weapons including attack helicopters and missiles
- Urging all states to inspect cargo suspected of containing banned items to and from Iran in their territory, including seaports and airports
- Calls on countries to block financial transactions and ban the licensing of Iranian banks if they suspect a link to nuclear activities
Turkey, Brazil and Lebanon are not expected to back this week's proposed UN resolution, but none of them has a veto.
Western diplomats expect 12 countries, including all five veto-holding permanent council members, to vote for the measure.
