“At the moment Iran has speeded up its enrichment activities, so Security Council resolutions have had a positive effect on this work,” Ali Asghar Soltanieh told the student ISNA news agency.
Uranium enriched to low levels makes nuclear fuel but in highly purified forms of more than 90 percent it can make the fissile core of an atom bomb.
Iran says it only wants the process to make nuclear fuel, denying allegations that its programme is a cover for a weapons drive.
The UN Security Council has imposed two sets of sanctions on Tehran for its continued refusal to suspend enrichment.
Soltanieh added that construction work on a heavy water reactor in Arak, in central Iran, was continuing without delay, despite International Atomic Energy Agency (IAEA) calls to halt the work.
“There has been no stop to our work in Arak,” he said.
“If the United States and the Europeans insist that Iran not have a heavy water reactor they should accept that we enrich uranium to a higher level.”
He said the Arak reactor, due to be completed in 2009, would replace a research reactor in Tehran which was supplied by the Americans before the 1979 Islamic revolution.
“At the time, 93 percent (enriched) fuel was supplied, and the next batch of fuel was 20 percent, it is not possible to go under this level,” Soltanieh said.
A senior diplomat with ties to the IAEA said that Iran was already operating more than 1,300 centrifuges for enrichment by mid-May at its Natanz plant and could have 3,000 by the end of July.
Under ideal conditions they could produce enough highly enriched uranium to produce a nuclear weapon within a year at most.
