Iranian officials have begun two days of nuclear talks with the International Atomic Energy Agency.
The nuclear watchdog will push for greater cooperation from Iran at the meeting in Vienna, Austria, the Associated Press reported.
The priority for the IAEA is to clarify whether Iran's nuclear program has any "possible military dimensions," said Deputy Director General Herman Nackaerts.
"It's important now that we can engage on the substance on these issues and that Iran let us access people, information, documents and sites."
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Specifically, Reuters said, the IAEA wants access to Parchin, a military complex south-east of Tehran where Iranian scientists are suspected to have tested explosives suitable for use in a nuclear weapon.
The government refused to allow IAEA inspectors to visit the site during their mission in Iran in February, which the agency's director general, Yukiya Amano, described as "disappointing."
Iran denies that it is seeking to develop nuclear weapons. Foreign Minister Ramin Mehmanparast has indicated that the government would allow inspections at Parchin "within the framework of an agreement between Iran and the agency," without giving further details.
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This week's talks come shortly before Iran is due to discuss its nuclear program with six world powers in the Iraqi capital, Baghdad, on May 23.
"Any miscalculation by the West will prevent the [Baghdad] negotiations from being successful," the secretary of Iran's Supreme National Security Council warned yesterday, according to the Tehran Times. Instead, Saeed Jalili said, "we will wait for a measure that will win the confidence of the Iranian nation."
US officials are nonetheless hopeful that mounting economic pressure due to sanctions will push Iran to make key concessions in Baghdad, according to the Washington Post.
The paper reported today that Iran has been switching off satellite tracking systems on its oil tankers since early April, in order to sidestep restrictions on its exports. The practice, illegal under maritime law, is being monitored by the International Energy Agency, the Post said.