International Atomic Energy Agency chief Yukiya Amano hailed "intensive" talks on Iran's nuclear programme during a visit to Tehran on Monday, state television said, but no progress was made on key inspection issues.
"We had expansive and intensive talks in a positive atmosphere," the broadcaster IRIB quoted Amano as saying.
The upbeat assessment was seen as significant ahead of broader, more substantive talks to take place on Wednesday in Baghdad between an Iranian delegation led by Jalili and representatives of world powers in the so-called P5+1 group.
"Certainly the progress of these talks will have a positive effect on Iran and the P5+1 negotiations. Of course these two issues are different from one another, but can underpin each other," Amano was quoted as saying.
Iranian officials, however, did not permit foreign journalists to approach Amano, so it was impossible to independently verify his comments.
Amano's reported comments gave no indication of agreement on specific areas the IAEA chief had set out to bridge.
A diplomatic source at IAEA headquarters in Vienna, speaking on condition of anonymity, said that, while Amano's talks had been good and could be followed with further discussions, no breakthrough was made.
IRIB said that Iran's lead nuclear negotiator, Saeed Jalili, lauded the "good talks" he had with Amano.
"We had very good talks with Amano and, God willing, we will have good cooperation in the future," he said.
And Foreign Minister Ali Akbar Salehi, after his own face-to-face with Amano, "expressed satisfaction over the opening of a new constructive path in Iran-agency cooperation" that "emanates from mutual trust and understanding."
Amano during his meetings discussed nuclear disarmament, halting nuclear weapons proliferation, and the peaceful use of nuclear energy as permitted under the nuclear Non-Proliferation Treaty, IRIB said.
There was also discussion of "consolidating" the UN nuclear surveillance agency to make it more effective in pursuing those goals, it added.
One area of contention was hinted at, however, when Amano reacted to Iran's insistence that a "road map" be established for its response to IAEA suspicions of nuclear weapons research.
"I will not get into details," he was quoted as saying. "The agency has its own view and Iran has its own."
That had bearing on the UN agency's demands -- repeatedly rebuffed by Tehran -- that it be given access to a key military installation, Parchin, outside Tehran, where the IAEA suspects explosives tests for nuclear warhead research have been conducted.
Iran says Parchin is not a designated nuclear site and thus it is not obliged to permit IAEA inspections, although it last did so in 2005.
It says if it did allow inspections of the site, they would have to be part of an agreed "road map" that would address the IAEA's concerns in a set order.
Iran has denied IAEA and Western suspicions that it has embarked on any nuclear weapons work.
Amano had said before leaving for Tehran that, while he was going into the discussions with a positive mindset, his one-day visit was too short to carry out in-depth work such as inspections.
The results of his talks will inevitably flow into the Baghdad discussions to take place on Wednesday between Jalili and representatives of the P5+1 -- comprising veto-wielding UN Security Council permanent members Britain, China, France, Russia and the United States, plus Germany.
A European diplomat in Brussels said, though, that the Western nations involved in the Baghdad talks were looking to Iran to halt its enrichment of uranium to 20 percent purity, which put it close to the 90 percent level needed to make atomic bombs.
Giving the IAEA access to Parchin would be "important but not sufficient," the diplomat said.
Iran, on its side, wants to see Western sanctions targeting its vital oil and financial sectors eased. Although Iranian officials insist they are having no effect, foreign analysts, traders and international agencies affirm the contrary.
Those sanctions are programmed to be ratcheted up further in just over a month's time, when US and EU measures aimed at blocking Iran's foreign oil sales come fully into effect.
The United Nations has also imposed its own set of sanctions on Iran in a series of resolutions that call for the Islamic republic to suspend all uranium enrichment -- something Tehran has repeatedly refused to do.
The spectre of military action against Iran by the United States or its ally Israel -- the sole if undeclared nuclear weapons state in the Middle East -- looms should the P5+1 nuclear talks fail to make headway.