With the second round of Iran's talks with world powers over its disputed nuclear program approaching next week, it remains unknown whether a deal can be cut to satisfy all sides.

Iran and six world powers -- Britain, China, France, Germany, Russia and the United States -- held talks earlier this month in a bid to reach a preliminary agreement on Iran's nuclear program. While the talks fell apart, a second round is slated for next Wednesday.

Western powers and Israel charge Iran with using its nuclear program to build weapons, and the talks are aimed at curbing Iran's nuclear program in exchange for easing the US-led sanctions that have crippled the Islamic Republic's economy.

"Quite frankly, in light of the gaps that blocked agreement at the end of the last round, securing a deal this time around seems iffy -- perhaps 50-50," former deputy director of the US State Department's Middle East Intelligence Office Wayne White told Xinhua.

Indeed, sparring continues over why exactly the first round failed, with Iran blaming the powers for being divided and the US saying Iran backed off from an agreement that went further than Tehran was willing to go.

Experts said the next meetings will likely focus on details such as demands that what Iran calls its right to enrich uranium be left out of any agreement. The discussions are also likely to see demands to halt work on Iran's controversial heavy-water reactor project at Arak in northwestern Iran.

If there is a compromise, Iran probably will have to limit its enrichment to 5 percent (reactor fuel), cap the number of its centrifuges, make additional concessions concerning the Arak facility, and perhaps commit to more transparency, White said.

In return, the world powers will have to recognize what Iran believes is its right to enrich to a limited degree, and perhaps be more forthcoming on sanctions relief, he said.

International Atomic Energy Agency (IAEA) Director Yukiya Amano said this week that while Iranian nuclear activities condemned under U.N. Security Council resolutions have continued, Iran's activities have not escalated.

Some observers have been encouraged by Iran's separate deal with the IAEA to grant access to sites such as the heavy-water reactor in Arak.

But White noted the IAEA deal only provided limited access to Iran's nuclear infrastructure, pointing out that the deal omitted access to Iran's Parchin complex, to which the IAEA has repeatedly requested access.

Some experts expressed optimism on a deal with Iran, despite problems in the recent talks. The world powers sought in the previous meeting a temporary curb on Iran's nuclear program in exchange for a temporary easing of sanctions on Tehran.

Writing for USA Today on Thursday, Brookings Institution's senior fellow Michael O'Hanlon argued that if the Arak reactor can be dismantled and the vast majority of the centrifuges either dismantled or destroyed, and Iran's stock of 20 percent U-235 converted into reactor fuel for a science reactor or for sale abroad, "that would be a good start on a fair deal."

Beyond that, O'Hanlon called on Iran to promise not to rebuild its stock of enriched uranium and allow international inspectors to monitor fixed nuclear sites while also following up leads on any suspected illicit sites.

If Iran agreed to that, most international sanctions and some US sanctions could be lifted over a period of months, he said.

Meanwhile, Israel's hardline Prime Minister Benjamin Netanyahu on Friday expressed grave concerns about the talks via his Twitter account, warning the powers to avoid a "bad deal." Israel is deeply worried that Iran's recent overture to Western powers is only a plot to rid itself of the crippling sanctions.

"The key here is really to find a way to reassure Israel," David Pollock, an expert at the Washington Institute for Near East Policy, told Xinhua.

"It's not so much about this deal, it's about what happens after this deal," Pollock said. "Because the deal, if they reach it, is explicitly defined as a temporary one."