Spotlight: Major countries, Iran try to iron out differences on nuclear deal as deadline approaches

As the March 31 deadline for a framework agreement on Iran's nuclear program is drawing near, six world powers endeavored to narrow down differences with Tehran on some key issues that may hamper the deal.

Senior officials from Iran and the P5+1 countries -- the United States, China, Russia, France, Britain, plus Germany -- on Wednesday kicked off a new round of nuclear talks in the Swiss city of Lausanne.

The talks were aimed at closing gaps in the positions between Iran and the world powers, as part of a prolonged negotiating process that could get Tehran to curb its nuclear activities for at least 10 years in exchange for the gradual lifting of the international community's economic sanctions.

Negotiations are expected to last until Friday, with each side hoping to resolve as many lingering issues as possible, from the speed of lifting sanctions to the level of inspections on Iran's nuclear sites.

Before Wednesday's talks, top U.S. and Iranian diplomats have held intensive bilateral meetings since Sunday. U.S. Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif met twice for more consultations.

Ali Akbar Salehi, head of Iran's Atomic Energy Organization, and U.S. Secretary of Energy Ernest Moniz also resumed technical negotiations.

Iranian state news agency IRNA quoted Zarif as saying that the nuclear talks have reached fine details which demand a lot of work.

"We are trying to narrow the differences on some issues," said the lead Iranian negotiator.

In Tehran, Marzieh Afkham, a spokeswoman for the Iranian Foreign Ministry, said that unless the negotiating parties agree on all the subjects of discussions, there would be no nuclear agreement.

"The talks have legal and complex dimensions and we have to wait for the developments in the following days," she said in a weekly press briefing when asked whether there is a chance for an agreement before the deadline.

She added that although the talks were complicated, the Iranian negotiating team had been trying to reduce differences with the world powers.

"We have had good progress in the technical aspects and most of the relevant problems have been solved," Afkham said, noting that the talks continued in the political and sanctions sectors.

It has been over 15 months since Iran and the world's major countries agreed to come back to the negotiating table to discuss the controversial Iranian nuclear program.

Iran claims its nuclear program is for peaceful purposes, but many in the West fear the country could eventually develop an atom bomb.

Under an interim deal between Iran and the P5+1 inked in November 2013, Iran said it would suspend critical nuclear activities in return for some easing of sanctions, with all sides seeking a final and comprehensive deal.

The six world powers have set a June 30 deadline to forge a final and comprehensive agreement, but the United States has said earlier that it hoped to reach a "framework agreement" by the end of March.

Kelsey Davenport, an expert with the U.S.-based think tank, the Arms Control Association, said all sides were making progress and they were closing the gaps on some of the most difficult issues, particularly in defining Iran's uranium enrichment program.

She added that the sticking points probably have to do with defining the size and scope of Iran's uranium enrichment.

"That's one of the most difficult issues to resolve in the talks from the technical perspective," Davenport said. Endi