By Fredrik Dahl
VIENNA (Reuters) - The U.N. nuclear watchdog signaled its determination on Monday to get to the bottom of suspicions that Iran may have worked on designing an atomic bomb, a day after Tehran agreed to start addressing the sensitive issue.
Chief U.N. nuclear inspector Tero Varjoranta said his team made good progress during February 8-9 talks in Tehran but that much work remained to clarify concerns about Iran's nuclear program in an investigation that Western diplomats say the Islamic state has long stonewalled.
"There are still a lot of outstanding issues," Varjoranta, deputy director general of the International Atomic Energy Agency (IAEA), said at Vienna airport after returning from the Iranian capital. "We will address them all in due course."
Iran denies Western allegations it seeks the capability to make nuclear weapons, saying such claims are baseless and fabricated by its foes. Years of hostile rhetoric and sabre-rattling raised fears of a wider war in the Middle East.
But a long moribund diplomatic push to resolve the decade-old dispute picked up steam after last June's election of a relative moderate, Hassan Rouhani, as Iran's president on a platform of conciliation to ease its international isolation.
In Tehran, Rouhani told a gathering of foreign diplomats that Iran's doors "are open to the IAEA within international regulations", the official news agency IRNA reported.
"We have never sought weapons of mass destruction. We don't want nuclear know-how for war, as some countries do," he said.
Iran and six powers struck an interim deal on November 24 to curb Tehran's nuclear work in exchange for some relaxation of sanctions that have hobbled the oil producer's economy and they will start talks next week on a long-term agreement.
The IAEA investigation into what it calls the possible military dimensions (PMD) to Iran's nuclear activity is separate from, but complementary to, the wider-ranging diplomacy between the Islamic Republic and the United States, France, Germany, Britain, Russia and China.
The IAEA investigation is focused on the question of whether Iran sought atomic bomb technology in the past and, if it did, to determine whether such work has since stopped.
Diplomats say the way the Iran-IAEA talks progress will be important also for the outcome of the big powers' diplomacy, which the West hopes will lead to a settlement denying Iran the capability to assemble a nuclear weapon any time soon.
"Continued progress on resolving PMD issues will go a long way to demonstrate to the international community that Iran is not pursuing nuclear weapons and is willing to come clean about its past activities," said Kelsey Davenport of the Arms Control Association, a U.S. research and advocacy group.
IAEA INQUIRY WILL "TAKE TIME"
The IAEA said on Sunday that Iran had agreed to take seven new practical measures within three months under a November transparency arrangement with the IAEA meant to help allay concern about the nuclear program.
For the first time and in a potential breakthrough, one of them specifically dealt with an issue that is part of the U.N. nuclear agency's inquiry into suspected atomic bomb research by Iran, which has repeatedly denied any such ambitions.
The IAEA said Iran would provide "information and explanations for the agency to assess Iran's stated need or application for the development of Exploding Bridge Wire detonators".
Although such fast-functioning detonators have some non-nuclear uses - including in the oil sector - they can also help set off an atomic device.
The Vienna-based U.N. agency has been investigating accusations for years that Iran may have coordinated efforts to process uranium, test explosives and revamp a missile cone in a way suitable for a nuclear warhead.
Faced with deadlock last year in its attempts to get Iran to cooperate with its investigation, the IAEA changed tactics and now seeks to gradually build mutual trust by starting with some of the less sensitive issues, diplomats say.
Suggesting that more difficult matters would have to wait a while longer, there was no mention in the IAEA's statement on Sunday of its long-sought access to the Parchin military base, where it suspects explosives tests relevant for nuclear bombs may have been conducted a decade ago. Iran denies this.
Other steps to be taken by Iran by mid-May under the agreement include IAEA inspector access to the Saghand uranium mine and design information about a planned reactor at Arak that the West fears could yield weapons material.
The IAEA, tasked with preventing the spread of nuclear weapons in the world, says it needs such information and access to get a more complete understanding of Iran's nuclear work, which Tehran says is aimed at generating electricity.
Varjoranta said Iran had implemented six previously agreed steps under the November framework accord, including providing inspectors access to two-nuclear related sites.
"Since November everything has gone as planned," he said, and more steps would follow. "These things take time."
(Additional reporting by Mehrdad Balali in Dubai, editing by Mark Heinrich)