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Associated Press
U.S. Wrestling executive director Rich Bender, right, shakes hands with President of the Iran's National Olympic Committee, Mohammad Aliabadi, as Iran's wrestling chief Hojatollah Khatib, left, looks on, in a meeting of representatives of FILA, the international wrestling federation, and world's wrestling powers, at the Parsian Azadi hotel, in Tehran, Iran, during wrestling World Cup tournament, Wednesday, Feb. 20, 2013. Arch foes Iran and the U.S. have found some common ground in the fight to save wrestling as an Olympic sport. The IOC, International Olympic Committee, executive board last week dropped wrestling from the program of the 2020 Games, a decision which brought a sharp backlash from wrestling organizations and national Olympic bodies around the world - including the United States, Russia and Iran. The man at second right, is unidentified.(AP Photo/Vahid Salemi)

VIENNA — In a disheartening signal to world powers at upcoming Iran talks, Tehran has started installing high-tech machines at its main uranium enrichment site that are capable of accelerating production of reactor fuel and — with further upgrading — the core of nuclear warheads, diplomats said Wednesday.

Iran already announced last week that it had begun mounting the new enriching centrifuges, but one diplomat said at the time that the announcement was premature with only a "small number" on site and not yet installed.

Diplomats told The Associated Press on Wednesday, however, that installation was now well on its way, with inspectors from the International Atomic Energy Agency seeing close to 100 or more machines mounted when they toured the site a few days ago. Depending on experts' estimates, the new-generation centrifuges can enrich uranium three to five times faster than Iran's present working model.

The Islamic Republic insists it is not working on a nuclear weapons program, but rather is enriching uranium only to make reactor fuel and for scientific and medical purposes — as allowed by international law.

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But many nations are suspicious because Iran went underground after failing to get international help for its uranium enrichment program in the 1980s, working secretly until its activities were revealed a decade ago. More recent proposals for international shipments of reactor fuel in exchange for Iranian enrichment concessions have foundered, with each side blaming the other.

Shrugging off demands to mothball enrichment — and growing international sanctions — Iran has instead vastly expanded the program to where experts say it already has enough enriched uranium for several weapons if the material is further enriched.