Iran, U.S., EU nuclear talks in Oman seen going to second day.....

(Reuters) - Iran, the United States and European Union will hold an unscheduled second day of talks on Monday on disagreements blocking resolution of a dispute over Tehran's nuclear program, a U.S. official and Iranian state media said.

With two weeks to a deadline for a comprehensive accord, Iranian Foreign Minister Mohammad Javad Zarif, U.S. Secretary of State John Kerry and EU envoy Catherine Ashton met in Oman's capital Muscat on Sunday to address a decade-long confrontation that has raised the risk of a wider war in the Middle East.

Reiterating Iran's official line, Ali Akbar Velayati, a top aide to Supreme Leader Ayatollah Ali Khamenei, was quoted by Iranian media as saying the Islamic Republic would not abandon its nuclear "rights" but was committed to the negotiations under Khamenei's leadership.

Western countries and close U.S. ally Israel suspect Iran has covertly sought to develop the means to build nuclear weapons.

Iran denies any secret nuclear weapons agenda, saying it wants peaceful nuclear energy only, but has refused to curb enrichment capacity and has been hit by damaging U.S., EU and U.N. Security Council sanctions as a result.

The discussions aim to put verifiable limits on Iran’s uranium enrichment work - and any other potential path to a nuclear weapon - in return for a gradual lifting of sanctions.

The negotiations at a luxury hotel appeared to be intense. The Iranian, U.S. and European delegations met from 11:30 a.m. to 2:30 p.m. local time, broke for lunch and consultations, and then resumed three-way talks just before 6 p.m. (1400 GMT).

"NO GOING BACK"

Both U.S. and Iranian officials said the discussions would continue on Monday, past the time when some of the participants were due to have left.

"Talks will continue in the morning," a U.S. official said.

"Talks between Kerry, Zarif and Ashton ... will continue on Monday, to narrow the gaps and reach a comprehensive deal by the Nov. 24 deadline," the official IRNA news agency reported.

Omani Foreign Minister Youssef bin Alawi gave reporters an upbeat assessment of the talks. "By the level of commitment all parties are showing, we feel comfortable," he said. "There is no going back ... I feel that all parties are positively willing to reach an agreement."

The thorniest unresolved issues are the size of Iran's enrichment program, the length of any long-term agreement and the pace at which international sanctions would be phased out, according to Western and Iranian diplomats involved in the negotiations.

Washington also wants intensive verification and monitoring measures to ensure Iran is living up to its end of the bargain.

As Kerry arrived in Oman, a senior U.S. official said the three-way talks would be "an important meeting," with the focus on making progress in order to meet the deadline.

U.S. officials say major gaps still remain in negotiating positions. Kerry said last week that the United States and its partners were not contemplating an extension of the Nov. 24 deadline, although he held out the possibility that negotiations could go beyond that date if major issues were resolved and there were only technical details to wrap up.

SOLUTION POSSIBLE

Speaking to Iranian state television on his arrival in the Omani capital Muscat on Saturday night, Zarif reiterated that sanctions imposed on Iran had brought "no result" for the West.

"If the West is interested in reaching such a solution, there is possibility to find a solution and to reach an understanding before November 24," he said.

Quoted by Iranian student news agency ISNA in Tehran, Velayati said Iran "will not abandon our rights" over nuclear facilities at Fordow, Natanz and Arak as well over the size of its centrifuge program that enriches uranium for nuclear fuel.

Centrifuges are machines that spin at supersonic speed to increase the ratio of the fissile isotope in uranium. Low-enriched uranium is used to fuel nuclear power plants, Iran's stated goal, but can also provide material for bombs if refined much further, which the West fears may be Iran's latent aim.

"We are committed to the talks and our negotiators are acting based on a framework ... outlined by the leader," he was quoted as saying, reinforcing the widely accepted notion that Khamenei has the last word on important matters of state.

A senior Iranian official close to the talks told Reuters the Oman talks would examine "the gaps that are still huge, Iran's enrichment capacity and time frame of lifting sanctions."

Iran's ties to the West have thawed since a centrist, Hassan Rouhani, was elected president last year to try to end Iran's international isolation. But Western officials say differences remain over how to guarantee Iran's nuclear path is peaceful.