VIENNA The U.N. nuclear watchdog is expected to publish intelligence soon pointing to military dimensions to Iran's nuclear activities but stopping short of saying explicitly that Tehran is trying to build atom bombs, Western diplomats say.
Russian and Chinese reluctance may frustrate any Western bid to seize on next month's report by the U.N. International Atomic Energy Agency (IAEA) to press for expanded United Nations sanctions on Iran, a major oil producer.
Moscow and Beijing signaled concern last week that the timing of the IAEA document could damage any chances for diplomacy to resolve the nuclear row.
In contrast, Western envoys believe the report -- which they portray as incriminating for Iran -- will pile further pressure on the country to curb its sensitive nuclear work and address international concerns about its aims.
"We are in favor of a strong report," one Western official said. "The IAEA has a lot of information that would allow the agency to come to clear findings on the issue of possible military dimensions" of Iran's nuclear program.
The different views indicate divisions among the six major powers involved in the search for a diplomatic solution to the long-running dispute over Iran's nuclear program -- the United States, Germany, France, Britain, China and Russia.
Western powers believe Iran is secretly trying to develop nuclear weapons, but Tehran denies this, saying it is enriching uranium only to power reactors for electricity generation.
Western diplomats say Russia and China may be unwilling to back any move at a mid-November meeting of the IAEA's 35-nation governing board to refer Iran once again to the U.N. Security Council, based on the agency's report.
"The follow-up to the next (IAEA) report is going to be critical, but it doesn't necessarily need to involve a new U.N. Security Council resolution," said analyst Peter Crail of the Washington-based Arms Control Association.
"If the details in the report do point to work on developing a nuclear warhead, the board members should adopt a resolution that at the very least condemns such activities and calls for Iran to cooperate with the IAEA investigation."
Russia, which has commercial and other links with Iran, has proposed a step-by-step effort to defuse the nuclear standoff, but Western diplomats have given the plan a cool response.
European Union leaders warned Iran Sunday it would face tougher sanctions if it failed to respond to concerns about its nuclear activities.
Two days earlier EU foreign policy chief Catherine Ashton -- who handles contacts with Iran for the six powers -- told Tehran that talks could resume soon if it was ready to "engage seriously in meaningful discussions."
NO SYRIA-STYLE CONCLUSION
IAEA Director-General Yukiya Amano said last month he would soon set out in greater detail the reasons for his growing concern that Iran may be working to develop nuclear weapons.
Western diplomats believe he will publish significant amounts of information on this in his next quarterly report on Iran's nuclear program, due in early November.
They say it is likely to include intelligence about work which can have both military and civilian uses, and work which would make little sense for activities not related to weapons development. It may also give names, locations and dates.
"Iranian experts have conducted experiments with neutron sources and highly explosive detonators that would only make sense for military applications," former IAEA deputy director general Olli Heinonen told Der Spiegel magazine.
For several years the IAEA has been investigating Western intelligence reports indicating that Iran has joined together efforts to process uranium, test high explosives and revamp a ballistic missile cone to accommodate a nuclear warhead.
The IAEA has said in previous reports that the data it has obtained about such issues is extensive and comprehensive, and also "broadly consistent and credible."
The IAEA has "received countless pieces of information on Iran's nuclear activities from governments and other sources," one Western envoy in the Austrian capital said.
Iran has routinely dismissed the accusations as baseless and forged, insisting its nuclear program is aimed at producing electricity so that it can sell gas and oil abroad.
But its history of concealing sensitive nuclear activity and its refusal to suspend work that can also yield atomic bombs have drawn four rounds of U.N. sanctions, as well as separate sanctions imposed by the United States and the European Union.
The United States has called on Amano to make his "best assessment" of whether there have been military dimensions to Iran's nuclear work and whether that may still be the case.
But several diplomats said he is unlikely to come to a conclusion regarding Iran as clear-cut as the one about Syria in a report in May, when he said a facility bombed by Israel in 2007 was "very likely" to have been a secret nuclear reactor.
Iran's nuclear activities are spread out geographically and any military work would take place in secrecy beyond the reach of U.N. inspectors.
"To come to a Syria-type conclusion ... is going to be difficult," said one nuclear expert who declined to be named.
(Editing by Tim Pearce)