The UN nuclear watchdog chief said on Tuesday he expected to sign a deal with Iran soon to ease investigation into suspected work on atom bombs, potentially brightening prospects for big-power talks with Tehran to stop a drift towards conflict.
Speaking on the eve of the Baghdad meeting where six powers will test Iranian willingness to put transparent limits on its nuclear programme, Yukiya Amano said his wish for access to an Iranian military site where nuclear weapons-relevant tests may have occurred would be addressed as part of the accord.
But the powers will be wary of past failures to carry out extra inspection deals between the International Atomic Energy Agency and Iran, and Western patience is wearing thin.
European sanctions to block Iran's oil exports are to take force in July and Israel has mooted military action. Iran, which denies any ambition to develop nuclear arms, has threatened reprisals and oil prices have risen on fears of a new Middle East war hitting a shaky world economy.
Amano himself acknowledged that "some differences" remained before the deal he hashed out during a rare visit to Tehran on Monday could be sealed, although chief Iranian negotiator Saeed Jalili had told him these would not prevent agreement.
"(A) decision was made to conclude and sign the agreement ... I can say it will be signed quite soon," Amano told reporters at Vienna airport after returning from Tehran.
The veteran Japanese diplomat described the outcome of his meetings in Iran as an "important development".
"We understand each other's position better."
Asked what differences persisted, Amano said only that they were "details of discussions on this document".
Underscoring Western scepticism arising from the checkered history of IAEA accords with Iran, the acting US ambassador to the Vienna-based agency called on Iran to cooperate immediately and substantively with UN inspectors.
"While we appreciate the efforts (by the IAEA) to conclude a substantive agreement, we remain concerned by the urgent obligation for Iran to cooperate fully with the verification efforts of the IAEA ... to resolve all outstanding concerns about the nature of its nuclear programme," Robert Wood said.
Amano did not repeat a remark attributed to him by Iranian state television on Monday that his talks in Tehran would have a "positive impact" on the global powers' session with Jalili in Baghdad on Wednesday.
Western diplomats voiced doubt later on Monday that any significant breakthrough towards resolving suspicions about Iran's nuclear intentions had indeed been made, and were awaiting clarification from Amano.
Jalili said after meeting Amano that Iran was "a serious supporter of ... global disarmament, confronting the spread of nuclear weapons and the usage of peaceful nuclear technology for (non-proliferation treaty) member states".
He held out the prospect of "good cooperation with the agency in the future in these areas," but pointedly said nothing about clearing up concerns about suspected nuclear weapons work.
Iran has for four years stonewalled IAEA requests for access to sites, especially the Parchin military complex outside Tehran, as well as nuclear scientists and documentation to verify intelligence reports about research and experiments pertinent to manufacturing nuclear explosives.
The Islamic Republic has long defied UN resolutions calling for a suspension of its uranium enrichment programme and unfettered access for IAEA inspectors. Tehran has insisted it seeks to use nuclear technology only for power generation and medical procedures.
Iranian officials have served notice that a rapprochement deal with the IAEA should lead to a quick relaxation of sanctions doing increasing damage to its economy, but Western diplomats ruled out any such gesture at the Baghdad meeting.
"We are not going to do anything concrete in exchange for nice words," a senior Western diplomat said.
Jalili will meet in the Iraqi capital with Catherine Ashton, the EU foreign policy chief heading a coalition of the five UN Security Council permanent members - the United States, Britain, France, Russia and China - plus Germany.
The powers' main priority will be securing Iranian agreement to halt the higher-grade uranium enrichment it started two years ago and has since expanded, shortening the time needed for a potential "breakout" of nuclear weapons.
Iran says it needs uranium enriched to a fissile concentration of 20 percent for its medical isotope reactor. Enrichment to 5 percent of fissile purity is suitable for power plant fuel, while 90 percent constitutes fuel for bombs.
Western diplomats said Iranian cooperation on such issues as IAEA access to Parchin was important but not sufficient. One said ahead of the Baghdad meeting: "The 20 percent enrichment has to be addressed as a priority."
Pressure for a diplomatic compromise has risen.
Escalating Western sanctions on Iran's economically vital energy exports, and threats by Israel and the United States of military action should diplomacy be deemed at a dead end, have helped drive up world oil prices, compounding the economic misery wrought by debt crises in many industrialised countries.
Israel is "highly sceptical" about the deal. "We are highly sceptical about this apparent agreement between the IAEA and Iran," an Israeli official told AFP, speaking on condition of anonymity.
"This apparent agreement with Iran only deals with IAEA supervision; it doesn't deal with the bigger issue: stopping Iran from developing a nuclear weapon."
Israeli Finance Minister Yuval Steinitz, a member of Prime Minister Benjamin Netanyahu's nine-member inner circle said "We are pretty suspicious."
"We have seen the Iranians playing hide-and-seek for years with the international community and the International Atomic Energy Agency," he told Israeli army radio.
"They stop enriching; afterwards they resume enrichment," he said.
He added that Iran had a history of violating agreements with the IAEA.
"We saw in the past how agreements between the IAEA and Iran were flagrantly violated by Iran," he said.
"We saw that specifically when they hid two nuclear facilities, one in Natanz and one near Qom. We saw the same with North Korea, which despite their agreement with the IAEA, continued to develop nuclear arms."
Addressing MPs at the parliamentary committee on foreign affairs and defence, a senior official within Israel's military intelligence services said Iran wanted to give the appearance of cooperation, in order to carry on with its nuclear programme.
"Iran wants talks to continue, to avoid being forced to close its Qom facility and to stop enriching uranium," said Brigadier General Itai Brun, who heads the research division, in comments communicated by a spokesman.
"We stand by what Prime Minister Netanyahu said last night: Iran must stop all enrichment, remove enriched material, and dismantle the site near Qom," the official said.
Israel says an atomic Iran would pose an existential threat to the Jewish state and has refused to rule out the option of a pre-emptive military strike on its nuclear facilities.