Iran confirmed yesterday that it had expanded its controversial uranium enrichment program, an Iranian news agency reported.

The semiofficial Iranian Students News Agency Wednesday quoted an informed source as confirming the second cascade had been installed two weeks ago at the Natanz pilot enrichment plant in central Iran.

"Soon after injection of the gas, we will obtain the product of the second ... cascade," ISNA quoted the source as saying.

An Iranian official told the media the actual enrichment work will begin next week when the new network of centrifuges is fed with a special uranium gas.

The news comes as the world's six biggest powers are discussing the details of sanctions they want to impose on Tehran.

Iran said its uranium enrichment program aims only to generate electricity, while the United States and others suspect it is a cover for building atomic weapons.

A draft UN resolution circulated by Germany, France and Britain would ban the sale of missile and atomic technology to Iran, and end most UN help for its nuclear programs.

Earlier this week, media reports said Tehran had begun "dry-testing" a second network, known as cascades, of 164 centrifuges to go with an initial cascade that yielded Iran's first batch of enriched uranium suitable for power plant fuel in April.