U.N. nuclear officials are trying to hammer out an agreement on whether to help Iran complete a nuclear reactor near Tehran.
The 35-nation governing board of the International Atomic Energy Agency is holding talks in Vienna (Austria) on the matter.
Iran says the Arak reactor will produce radioactive isotopes for medical uses. But plutonium, which can be used for atomic bombs, will be a by-product.
The debate over help for the Arak reactor has become contentious, with western nations opposed and some developing nations in favor.
The U.S. ambassador to the International Atomic Energy Agency Gregory Schulte, says the United States opposes Iran's request.
Iran's envoy, Ali Asghar Soltanieh, has accused the West of politicizing a technical issue.
Major powers accuse Iran of planning to build nuclear weapons, a charge Iran denies.
In Tehran, Iranian President Mahmood Ahmadinejad said Monday his country will be self-sufficient in nuclear fuel within a year.
Iran says the Arak reactor is due to go online by 2009. It says it will pursue the project whether or not the IAEA helps.
The IAEA board is considering this week hundreds of requests for technical aid from countries pursuing peaceful uses for nuclear power. The board routinely approves such requests.
But earlier this year, the IAEA suggested Iran should abandon the Arak project.
In August, Iran defied a United Nations deadline to cease enriching uranium. The U.N. Security Council is considering sanctions against Tehran.
Some information for this report was provided by AFP, AP and Reuters.