LONDON - More than two years of negotiations on the future of Iran’s nuclear program, and international economic sanctions against it, face a deadline next Tuesday, with the two sides still reported to be far apart on several key issues.

Negotiators from Iran and the six countries deputized by the U.N. Security Council have been meeting regularly to prepare for foreign ministers to join the talks in Vienna, including Iran’s Mohammed Javad Zarif and U.S. Secretary of State John Kerry.

Issues Remain as Iran Deadline Looms

A senior U.S. administration official said Thursday negotiators are expected to be "close" to an agreement on the 30th, if they "can get there at all."

Issues Remain as Iran Deadline Looms

Those involved are predicting the talks will run past the deadline, perhaps by several days, but they also say another lengthy extension is not likely. There have already been two.

Issues Remain as Iran Deadline Looms

A top Western diplomat, speaking to reporters on condition of anonymity in Vienna, said Friday that major differences remain

The diplomat said the most difficult issues must be resolved in the coming days including U.N. inspections of Iran's sites, transparency, sanctions and the possible military dimensions of Iran's atomic program.

The stakes are high, with Western officials saying that without an agreement Iran could resume enriching uranium and could have enough fuel for a nuclear weapon within months.

But that would also mean a further toughening of the sanctions, which have already crippled Iran’s economy.

The negotiators from the five permanent Security Council Members – the United States, Britain, France, China and Russia – plus Germany are known as the P5+1. The delegation is chaired by the European Union’s foreign policy chief.

They reached an accord with Iran on key principles three months ago, which, according to details published by the U.S. delegation, appeared to indicate agreement on several contentious points.

But experts said the document also papered over continuing disagreements.

On June 23, with just a week to go before the deadline, the ongoing disputes came into the open in a speech by Iran’s Supreme Leader, Ayatollah Ali Khamenei. He took a tough line on several of them.

?In previous statements Khamenei has expressed support for the talks, at least to the extent of allowing his negotiators to see what they could achieve.

Analysts point out that the ayatollah has to address several audiences, including hard-liners in Iran who oppose any deal to limit the country’s nuclear program, and particularly do not trust the United States.

But such specific statements from the Supreme Leader that appear to rule out compromise on key issues, and even to backtrack on existing understandings, have officials worried.

Still, Ariane Tabatabai, visiting assistant professor of security studies at Georgetown University in Washington, D.C., said while appearing to take a hard line, the ayatollah has carefully left the negotiators some options.

“Over the years, every time he has come out and said things they have been packaged in a way that has given the negotiators the ability to maneuver,” she told VOA via Skype.

Tabatabai said although Khamenei is Iran’s Supreme Leader, Western officials tend to give too much credence to every statement he makes.

“People think that whenever Khamenei comes and says something, that’s it, it’s a very clear red line,” she said. “And it’s not. So far, it has not been.

“A careful examination of everything he has said and everything that has been achieved so far shows that not everything he says ultimately translates into policy,” Tabatabai added.

She noted, in the past, the ayatollah has cited specific figures for the number of nuclear enrichment centrifuges Iran must have, and then negotiators have agreed to much lower numbers.

Tabatabai also said Khamenei has accepted more intrusive inspections than he said he would.

In both cases, she said, some observers predicted the negotiations would break down, and they didn’t.

P5+1 negotiators will certainly be hoping these latest statements follow the same pattern.

A prestigious group of former U.S. officials has warned that if the international negotiators don’t insist on terms the ayatollah opposes, the final document “may fall short of meeting the administration’s own standard of a

The open letter published by the Washington Institute for Near East Policy, is signed by 18 people, including retired general and former CIA Director David Petraeus, former vice-chairman of the Joint Chiefs of Staff retired General James Cartwright, former Middle East negotiator Dennis Ross and Stephen Hadley, who served as national security adviser to former President George W. Bush.