Mohammed Ameen / AP
Iraq's Foreign Minister Hoshyar Zebari, second right, walks with the EU foreign policy chief Catherine Ashton upon her arrival at Baghdad International Airport on Wednesday for multi-party nuclear talks.
Updated 5:30 p.m. ET: BAGHDAD -- Iran and world powers exchanged unusually detailed proposals at talks in Baghdad on Wednesday in hopes of defusing a long, volatile standoff over suspicions Tehran's atomic energy program may be a disguised quest for nuclear weapons.
The stakes could hardly be higher: global oil markets are jittery over extended Western sanctions imposed on Iran's vital crude exports and the specter of a Middle East war arising from possible Israeli strikes against its defiant arch-enemy.
But no breakthrough appeared to be in the offing in Baghdad, where the six powers were testing Iran's willingness to curb its uranium enrichment work. Differences remained, notably, over when Iran would be rewarded with relief from economic sanctions.
A Western official said the discussions would resume on Thursday. He was speaking after Iranian chief negotiator Saeed Jalili and European Union foreign policy chief Catherine Ashton held a bilateral meeting that went on late into the evening.
After a 15-month diplomatic freeze and exploratory talks in Istanbul last month, envoys for Iran and the United States, Russia, China, France, Britain and Germany convened with both sides publicly upbeat about the scope for an outline deal.
"The EU three-plus-three side put forward a detailed proposal, which includes confidence-building measures that can pave the way for Iran to demonstrate that its nuclear program is for peaceful purposes and for it to comply with its UNSC obligations,” U.S. State Department spokeswoman Victoria Nuland said, NBC News reported. “And then this approach would also include step-by-step reciprocal steps aims at near-term action on our part if Iran takes it own steps.”
Former Secretary of Defense William Cohen talks about the significance of Ryan Crocker's departure as U.S. ambassador to Afghanistan. Cohen also comments on the ongoing nuclear talks with Iran.
The end goal for Washington is "full compliance by Iran with its international obligations and full ability of the IAEA to inspect and verify any obligations that it has undertaken," Nuland said.
Iranian media close to the Tehran government said Jalili presented a five-point package covering a "comprehensive" range of nuclear and non-nuclear issues.
The official news agency IRNA sounded a note of discord by quoting Iranian officials as referring to the big-power proposal as "nitpicking" while student news agency ISNA said: "Apparently from the Iranian point of view this package is not balanced."
However, those leaks did not appear to be Tehran's final response as the talks ran on into the evening.
The powers' overall goal is an Iranian agreement to curb uranium enrichment in a transparent, verifiable way to ensure it is for peaceful purposes only. Iran's priority is to secure an end to sanctions isolating the country and damaging its economy.
The pivotal proposal by the six, led by Ashton, was for Iran to halt its enrichment of uranium to the higher fissile concentration of 20 percent, her spokesman Michael Mann said as talks got under way.
That is the Iranian nuclear advance most worrying to the West since it largely overcomes technical obstacles to reaching 90-percent, or bomb-grade, enrichment. Iran says it is enhancing the fissile purity to such a degree only for medical research.
"We have a new offer on the table which addresses our main concerns about the Iranian nuclear program. The 20-percent enrichment question," Mann told reporters. "We hope the Iranians respond positively and we can make progress today."
In a separate interview with Iran's state-run English-language Press TV, Mann said no final deal was expected in Baghdad because progress was likely to be only gradual.
He said toughened sanctions, especially an EU ban on Iranian oil exports due to take full effect on July 1, had helped to draw Iran finally into serious negotiations.
Iran has hinted at flexibility on higher-grade enrichment although analysts caution that it would be unlikely to compromise much while sanctions remain in place.
In previous meetings the two sides could not even agree an agenda, with each largely repeating known positions and Tehran refusing any dialogue on changes to its nuclear path.
Iranian Foreign Minister Ali Akbar Salehi, speaking to reporters in Tehran, said: "The ideas fielded to us speak of the fact that the other side would like to make Baghdad a success. We hope that in a day or two we can bring good news."
Salehi also warned that Iran would not bow to pressure: "Their policies of pressure and intimidation are futile. They have to adopt policies to show goodwill to solve this issue."
NBC News’ Catherine Chomiak contributed to this report from Reuters.
More world news from msnbc.com and NBC News:
- 'Boiling point': On Lebanon’s Syria Street, a mini-civil war brews
- Africa's Rainbow Nation troubled by racist time warp
- 'Nearly empty': A rare glimpse inside Syria rebel stronghold
- Terror suspect's eye color? UK's flying cameras know
- Analysis: How Egypt's election can transform the Middle East
Follow us on Twitter: @msnbc_world