Iran nuclear talks extended until April 1

Negotiations for a nuclear deal between Iran and six world powers have missed the March 31 deadline for a framework agreement and have been extended until Wednesday, according to media reports.

In spite of a full day of talks on Tuesday, the negotiators -- the P5+1 group of countries (the US, Britain, China, Russia, France, plus Germany) and Iran -- were still working to resolve several issues, a US official said, according to a New York Times report on Tuesday.

"We've made enough progress in the last days to merit staying until Wednesday," said US state department spokesperson Marie Harf. "There are several difficult issues remaining."

Any accord that is reached will be, by design, an interim instrument that may be devoid of some specifics that the US Congress, Israel, Arab states, and Iran's military and hard-liners have been worried about.

The March 31 deadline was set three months back as a mechanism to determine whether there was enough political will to reach a final accord by the end of June, when an interim agreement temporarily limiting Iran's nuclear activities would expire.

A few days ago, Iran seemed intransigent on several major issues. It wanted UN sanctions to be lifted almost immediately, while the US and its negotiating partners wanted any relaxation to be gradual, in order to ensure that Iran took steps that would make it far harder to produce bomb-grade nuclear material in less than a year, as it answered long-evaded questions from international inspectors.

On Monday, the US state department acknowledged that the issue of Iran's large stockpile of nuclear fuel remained a subject of debate.

"The bottom line is that we don't have agreement with the Iranians on the stockpile issue," Harf said.

"One person is missing here: It's Ayatollah Khamenei," a senior European diplomat said on Monday, referring to the Iranian supreme leader. "We don't know what he will think of the provisions."

Also missing is the US Congress, which has pledged to impose additional sanctions if a preliminary accord is not reached -- a threat that may lead the Obama administration to solidify what it could get now and seek more in the next three months.

The issues the negotiators have been struggling to resolve include the pace at which the UN sanctions would be lifted, restrictions on research and development related to new types of centrifuges, and the length of the agreement.