The UN Security Council is set to slap new sanctions on Iran Wednesday for refusing to rein in its suspect nuclear program, despite warnings from Tehran it will break off talks on the standoff.

After months of behind-the-scenes haggling, Mexican Ambassador Claude Heller, who chairs the 15-member council this month, said a draft resolution on fresh sanctions would go to a vote on Wednesday at 10:00 am (1400 GMT).

"I think it is fair (to say) that these are the most significant sanctions that Iran has ever faced," US Secretary of State Hillary Clinton told reporters during a visit to Ecuador.

The resolution's six co-sponsors -- the five council permanent members Britain, France, China, Russia and the United States along with Germany -- say they have more than the nine votes needed to adopt the text.

It would be the fourth set of UN sanctions imposed on Iran in recent years, as the international community has struggled -- and failed -- to curb the Islamic republic's nuclear ambitions.

Iran insists its uranium enrichment program is for peaceful civilian purposes, while the Western nations have led accusations that it is seeking to develop an atomic weapon.

According to the US-drafted text, the resolution would broaden three earlier sets of sanctions slapped on Iran, the last of which adopted on March 3, 2008.

The new resolution:

-- Would expand an arms embargo and measures against Iran's banking sector and ban it from sensitive overseas activities like uranium mining;

-- Authorize states to conduct high-sea inspections of vessels believed to be ferrying banned items from or to Iran;

-- Add 40 entities to a list of people and groups subject to travel restrictions and financial sanctions, as well as Javad Rahiqi, head of Atomic Energy Organization of Iran's Isfahan nuclear technology center.

According to the draft text, 22 of the entities are linked to Iran's nuclear and ballistic missile programs, 15 are "owned, controlled, or acting on behalf of the Islamic Revolutionary Guard Corps" and three are controlled by the Islamic Republic of Iran Shipping Lines.

Iranian President Mahmoud Ahmadinejad has angrily warned that negotiations with the six major powers on his country's suspect nuclear program would be terminated if the new sanctions are imposed.

"I have said that the US government and its allies are mistaken if they think they can brandish the stick of resolution and then sit down to talk with us, such a thing will not happen," Ahmadinejad said in Istanbul.

A Turkish diplomat told AFP on condition of anonymity that Ankara was trying to persuade Iran not to abandon talks if sanctions were imposed.

Russian Prime Minister Vladimir Putin, whose country has decided to back the UN moves, said however the sanctions should not be extreme.

"Our point of view is that these decisions should not be excessive and should not put the Iranian people in a complicated position which would put up barriers on the path to peaceful nuclear energy," Putin was quoted by Russia's ITAR-TASS as saying.

US ambassador to the UN, Susan Rice, said Washington still hoped "to persuade Iran to halt its nuclear program and negotiate constructively and in earnest with the international community."

"We remain committed to the dual-track approach" of pressure through sanctions coupled with negotiations, she added.

Ahmadinejad however urged Western powers not to dismiss a Turkish-Brazilian nuclear fuel swap brokered last month which he described as an opportunity that should be "put to good use."

"Opportunities will not be repeated," he warned on the sidelines of a regional meeting.

Brazil and Turkey have pushed for an open debate in the Security Council on the nuclear standoff with Iran before the vote to make their case that sanctions will be counterproductive.

Under the deal they brokered, Iran agreed to ship 1,200 kilograms (2,640 pounds) of its low-enriched uranium (LEU) to Turkey in return for high-enriched uranium fuel for a Tehran reactor that would be supplied later by Russia and France.

But the six world powers which have been trying to clip Iran's nuclear ambitions only greeted the deal coolly.

In a nod to Brazil and Turkey, the draft UN text does note the efforts of the two countries "toward an agreement with Iran on the Tehran Research Reactor that could serve as a confidence-building measure."

It remained unclear whether Brazil, Turkey and Lebanon will vote against the new UN resolution or abstain.