Iran nuclear talks: What world powers are offering, Iran isn't buying. Yet.

Iran has been desperate for years to acquire spare parts for its aging fleet of civilian aircraft. But does it want those parts badly enough to get them in exchange for giving up its prized stockpile of 20-percent-enriched uranium?

Apparently not. Or at least, not so far. That is one reason that talks between Iran and the US and other world powers on Iran’s nuclear program ended Thursday without any agreement – except to reconvene the talks in Moscow next month.

The two days of talks in Baghdad failed to narrow differences between the two sides over how a deal easing international tensions over Iran’s nuclear program should look.

Iran wants a significant easing of the existing and looming sanctions on its economy, including its life-blood petroleum industry, in exchange for any concessions. But world powers want Iran to give up its stockpile of uranium enriched to 20 percent purity – a level that can be further purified relatively quickly to the 90-percent-enriched uranium to fuel a nuclear weapon – but without any roll-back of sanctions, at least initially.

The proposal presented to Iran includes a list of other incentives, and that’s where the airplane parts come in. But so far Iranian officials are scoffing at the seriousness of the proposal presented by the European Union’s foreign policy chief, Catherine Ashton, who is leading negotiations for the world powers.

“Giving up 20 percent enrichment levels in return for plane spare parts is a joke,” Hassan Abedini, an executive with Iranian state-run media who was briefed on the talks, said in comments to the Associated Press.

The Iranians want an immediate easing of sanctions to be part of any deal, but so far the world powers – the US, Russia, China, Britain, France, and Germany – are not biting. US officials insist privately that it was the increasingly severe sanctions that brought the Iranians to the table in the first place.

In comments to reporters in Washington Thursday after the conclusion of the Baghdad talks, Secretary of State Hillary Rodham Clinton was adamant that sanctions would not be eased any time soon – certainly not before talks reconvene in Moscow June 18.

“As we lay the groundwork for these talks, we will keep up the pressure,” she said. “All of our sanctions will remain in place and continue to move forward during this period.”

Yet even amid the refusals to budge on both sides, the discussions were apparently promising enough for the parties to agree to keep the talks going.

“It is clear that we both want to make progress, and that there is some common ground,” Lady Ashton told reporters following the talks. Despite the “significant differences [that] remain,” she added, “we do agree on the need for further discussion to expand that common ground.”

The world powers may see some advantage in allowing three weeks to go by before talks reconvene – for one thing, that will take Iran closer to imposition of the European Union’s embargo on Iranian oil imports, and deeper into US sanctions on its central bank.

But the delay also involves some risk – in particular that Israel, and allied members of Congress, will dismiss the extended time frame for negotiations as merely an opportunity for Iran to continue enriching uranium and progressing towards “nuclear weapons capability.”

And that could prompt Israel to renew its threats of launching air strikes on Iranian nuclear facilities. Already on Wednesday, Israeli Defense Minister Ehud Barak said that an agreement by Iran to open its facilities to more intrusive United Nations inspection would not be enough for Israel to desist from weighing military options.

In her remarks, Secretary Clinton appeared to try to address anticipated criticisms of the negotiations calendar by emphasizing what she called the unprecedented unity of the world powers in their approach to Iran.

“I think if you had asked three and a half years ago, certainly when I started this job, could we have unity around some very difficult issues with Iran and have everybody onboard speaking literally off the same page with the same voice, there would have been a certain level of skepticism,” she said.

The question now will be whether that “unity” that includes Russia and China, traditionally more sympathetic to Iran’s perspective on its nuclear program, will be enough to cool demands for not just talks but action on Iran.