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Ronald Zak, Associated Press
Herman Nackaerts of the International Atomic Energy Agency, IAEA, Deputy Director General and Head of the Department of Safeguards, speaks to the press before his flight to Iran, at Vienna's Schwechat airport, Austria, Wednesday, Dec. 12, 2012 .

VIENNA — International officials engaged in a two-pronged effort Wednesday to engage Iran over concerns the country may have worked on nuclear weapons, with a U.N. team seeking access to a site linked to such suspected activity and European Union negotiators looking to restart talks with Tehran meant to ease such fears.

Preparing to depart Vienna for Tehran, Herman Nackaerts of the International Atomic Energy Agency signaled impatience with Iran's refusal to meet IAEA requests for information on its suspicion that the Islamic republic had researched and developed components of a nuclear weapons program. In brief comments, he noted "negotiations for almost one year" have already been conducted on the issue.

Nackaerts, who heads the IAEA's nuclear investigation, also told reporters his team was "ready to go" to Parchin, an Iranian site it suspects could have been used for such experiments, just as soon as Tehran approves a visit. In Tehran, he will push IAEA requests for access to information, officials and locations the agency thinks may have been used for weapons work.

Iran says it does not want atomic arms and justifies delays in cooperating with the IAEA by saying that a framework regulating the agency's probe must be agreed on first. But as the negotiations on such an agreement drag on, agency officials have complained that it is nothing more than a delaying tactic. They are particularly concerned that such delays can hurt their efforts to investigate Parchin.

In Tehran, Iranian President Mahmoud Ahmadinejad said Wednesday he had already announced back in 2007 that Iran had "become nuclear" by mastering all aspects of peaceful atomic technology.

"Efforts to prevent Iran from achieving this capability are (thus) irrelevant," he said in comments on his website. "So, it's better to cooperate and work together."

The IAEA suspects that Iran has conducted live tests of conventional explosives there that could be used to detonate a nuclear weapon and cites satellite photos indicating a cleanup of the site at a sprawling military base southeast of Tehran. Iran denies it is sanitizing the site, but IAEA chief Yukiya Amano has warned that his agency's chances of a meaningful investigation at Parchin are diminishing the longer the alleged cleanup continues.

The international community is also concerned about Iran's uranium enrichment — a program Tehran says is geared only toward making reactor fuel. But enrichment can also create the core material of nuclear weapons.

While developing nations insist Iran has a right to enrichment, Western governments and Israel fear it could be a cover for weapons aspirations — concerns fed by Iran's decision to boost enrichment grades last year to a level that is only a technical step short of weapons-grade uranium.

Six world powers have in recent months been developing a new approach to persuade Iran to curb at least higher-level enrichment. These include the possible easing of international sanctions crippling Tehran's oil sales and financial dealings, if it compromises.

In Brussels, an EU official said that Helga Schmid, deputy director of the European Union's diplomatic corps, spoke on the phone with Ali Bagheri, Iran's deputy nuclear negotiator, to discuss dates and venues for a new meeting with Iranian negotiators.

The official said the six countries negotiating with Iran remain united in seeking a diplomatic solution to the nuclear issue. The countries are France, Germany, Britain, China, Russia and the U.S. The official spoke on condition of anonymity because he was not authorized to discuss the matter.

Associated Press writers Don Melvin in Brussels, and Ali Akbar Dareini in Tehran, Iran, contributed to this report.