Diplomats to the UN atomic watchdog are bracing for a new report this week providing fresh detail on Iran's suspected nuclear weapons drive, amid growing speculation of an Israeli military strike.
Previous International Atomic Energy Agency (IAEA) assessments have centred on Iran's efforts to produce fissile material -- uranium and plutonium -- that can be for power generation and other peaceful uses, and also in a nuclear bomb.
But the new update, which diplomats say will be circulated among envoys on Tuesday or Wednesday, will focus on Iran's alleged efforts to put the radioactive material in a warhead and to develop missiles to carry them to a target.
"The report is not going to include some sort of 'smoking gun'," one Western diplomat told AFP. "But it will be an extensive body of evidence that will be very hard for Iran to refute as forgery, as they have done in the past."
IAEA head Yukiya Amano said in a September report he was "increasingly concerned" about the "possible military dimension" of Iran's atomic activities, calling information at the agency's disposal "extensive and comprehensive."
Western envoys hope the new information will help convince other countries of the need to pile yet more pressure on the Islamic republic, which has been hit with four rounds of sanctions by the UN Security Council.
But Russia and China, which have tended to take a softer line on Iran than fellow permanent Security Council members -- the United States, France and Britain -- are unconvinced on the need for more action, diplomats say.
Moscow has even gone so far as to call on the IAEA not to release the report, saying it would "hardly be timely ... [and] would without a doubt strain the atmosphere and may hinder the start of serious negotiations."
As a result, it is unclear what kind of resolution, if any, the 35-nation IAEA board will adopt -- a simple majority suffices, unlike the Security Council where permanent members can veto -- when it meets on November 17-18, experts said.
One option could be reporting Iran to the Security Council again, while another could be giving Tehran a deadline of until the next board meeting, for example, due in March, to address the watchdog's concerns, diplomats said.
"Would it be worth it to again divide the board on this issue, and also divide the E3+3?," the five Security Council permanent members plus Germany, said Oliver Thraenert from the German Institute for International and Security Affairs (SWP).
"To me that would not make much sense, although much will depend on the exact language of the report," he told AFP.
In either case, the release of the IAEA report comes at a time of growing speculation that Israel is running out of patience and might launch a military strike in an attempt to knock out its arch foe's nuclear activities.
Israeli daily Haaretz reported last week that Prime Minister Benjamin Netanyahu was seeking cabinet backing for a military strike, and that the new UN watchdog report would have a "decisive" effect on their policy.
On Friday President Shimon Peres was quoted as saying he believed Israel, which last week carried out rocket tests, is closer to using the military option than it is to finding a diplomatic solution.
Peres said late Saturday on Israeli private television's second channel "an attack on Iran" by Israel and other countries was "more and more likely."
Washington, meanwhile, has said that while the focus is on a diplomatic solution, all options are still on the table.
The US plans to bolster its military presence in the Persian Gulf after withdrawing from Iraq this year, and to expand military ties with the Gulf Cooperation Council, The New York Times reported last month.
And Britain's armed forces are making contingency plans for possible participation in an aerial attack on Iran's nuclear enrichment plants, according to the Guardian daily.