VIENNA, Aug. 9 (Saba) -- Iran has used a second set of centrifuge machines to enrich uranium to 20 percent purity at its Natanz facility, the International Atomic Energy Agency (IAEA) said on Monday, according to Xinhua.

The move would make Iranian efforts to enrich uranium to higher levels more efficiently, said the Vienna-based UN nuclear watchdog.

Western countries have long suspected Iran is trying to build nuclear bombs under the cover of a nuclear energy program. However, Iran insists its enrichment activity is only for peaceful purpose.

Iranian Foreign Minister Manouchehr Mottaki said on Sunday Iran is ready to participate in negotiations based on a nuclear fuel swap deal.

Iran, Turkey and Brazil signed an agreement on May 17, in which Iran committed itself to giving 1,200 kg of its 3.5-percent enriched uranium to Turkey in exchange for 20-percent enriched uranium to be used as fuel in the research reactor in Tehran.

Saba