IENNA (AP) -- A senior U.N. nuclear official said Sunday he hoped for progress in upcoming talks with Iran about suspected secret work on atomic arms, but his careful choice of words suggested little expectation that the meeting will be successful.
The comments by Herman Nackaerts as his International Atomic Energy Agency team prepared to leave for Tehran for the second time in less than a month appeared to reflect IAEA reluctance to raise hopes that Iran will engage on an issue that it claims has no substance.
Before the trip, senior diplomats told The Associated Press that Russia and China - strategic and economic partners which Iran traditionally relies on to blunt Western pressure over its nuclear activities - were urging Tehran to cooperate with the IAEA team.
Moscow and Beijing are "using some pretty high-level diplomacy" to persuade Iran, said one of the diplomats, who asked for anonymity in exchange for discussing confidential information coming from his capital.
Still hopes were slim. A previous IAEA mission returned from Tehran on Feb. 1 without managing to dent Iran's wall of denial. In comments to reporters at Vienna airport, Nackaerts was at pains to avoid raising hopes.
"Importantly, we hope that we can have some concrete results after this trip, and the highest priority remains of course the possible military dimensions of Iran's nuclear program," he said. "This is of course a very complex issue that may take a while, but we hope it will be constructive."
Iran has refused to discuss the alleged weapons experiments for nearly four years, saying they are based on "fabricated documents" provided by a "few arrogant countries" - a phrase authorities in Iran often use to refer to the U.S. and its allies.
Faced with Iranian denial, the IAEA summarized its body of information in November in a 13-page document drawing on 1,000 pages of intelligence. It stated then for the first time that some of the alleged experiments can have no other purpose than developing nuclear weapons.
The IAEA team wants to talk to key Iranian scientists suspected of working on a weapons program. They also hope to break down opposition to their plans to inspect documents related to nuclear work and secure commitments from Iranian authorities to allow future visits.
But before the trip, senior diplomats told the AP that Iran had made no commitments - despite the Russian and Chinese attempts at persuasion and a rapidly growing series of international sanctions threatening to choke Iran's oil lifeline and financial system.
The most recent squeeze on Iran was announced Friday, when SWIFT, a financial clearinghouse used by virtually every country and major corporation in the world, agreed to shut out the Islamic Republic from its network.
Tehran remained defiant Sunday, announcing has halted oil shipments to Britain and France, in an apparent pre-emptive blow against the European Union after the bloc imposed sanctions on Iran's crucial fuel exports.
At the same time, it appeared eager to show it was ready to talk. Even before receiving an answer on its offer last week to meet with world powers on its nuclear program, Foreign Minister Ali Akhbar Salehi on Sunday set Istanbul, Turkey, as the venue of those negotiations.
Beyond concerns about the purported weapons work, Washington and its allies want Iran to halt uranium enrichment, which they believe could eventually lead to weapons-grade material and the production of nuclear weapons. Iran says its program is for peaceful purposes - generating electricity and producing medical radioisotopes to treat cancer patients.
Its activities at its plant at Fordo, near the holy city of Qom are of particular concern because it is dug into a mountain and possibly impervious to attack - an option that both Israel and the United States refuse to rule out should diplomatic persuasion and sanctions fail to stop Tehran's nuclear drive.
Reflecting growing jitters that the Israelis are poised to strike, both U.S. and Britain on Sunday urged Israel not to attack Iran's nuclear program.
The U.S. joint chiefs of staff, Gen. Martin Dempsey, and British Foreign Minister William Hague said an Israeli attack on Iran would have grave consequences for the entire region and urged Israel to give international sanctions against Iran more time to work. Dempsey said an Israeli attack is "not prudent," and Hague said it would not be "a wise thing."
In interviews Friday and Saturday, diplomats told the AP that Iran is poised to install thousands of new-generation centrifuges at the cavernous facility - machines that can produce enriched uranium much more quickly and efficiently than its present equipment.
While saying that the electrical circuitry, piping and supporting equipment for the new centrifuges was now in place, the diplomats emphasized that Tehran had not started installing the new machines and could not say whether it was planning to.
Still, the senior diplomats - who asked for anonymity because their information was privileged - suggested that Tehran would have little reason to prepare the ground for the better centrifuges unless it planned to operate them.