Nuclear talks in Geneva
Nuclear talks in Geneva Reuters

Iran’s Supreme Leader is not alone when he expresses skepticism about talks between his country and the six world powers.

A senior United States official quoted by the Reuters news agency said on Monday that talks between Iran and the P5+1 on a long-term deal for Tehran to limit its nuclear program and see international sanctions lifted will be long and complicated with no guarantee of success.

The remarks on the eve of the first round of high-level negotiations since an interim deal struck on November 24 under which Tehran curbed some nuclear activities for limited sanctions relief.

"These next days this week are the beginning of what will be a complicated, difficult and lengthy process," the administration official, who spoke on condition of anonymity, told reporters in Vienna.

"When the stakes are this high and the devil is truly in the details, one has to take the time to ensure the confidence of the international community in the result," the official added. "That can't be done in a day, a week or even a month in this situation."

Senior officials from Britain, China, France, Germany, Russia and the United States will begin several days of talks in Vienna on Tuesday with an Iranian delegation led by Foreign Minister Mohammad Javad Zarif and his deputy Abbas Araqchi.

European Union foreign policy chief Catherine Ashton will oversee the talks, which will be the first in what is expected to be a series of meetings in the coming months.

The six-month interim nuclear deal between Iran and the P5+1 went into effect on January 20.

Under the agreement, Iran committed to limit its uranium enrichment to five percent, halting production of 20 percent-enriched uranium. In return, the European Union and the United States have eased crippling economic sanctions on Iran.

Iran has already received the first installment of $4.2 billion in frozen assets.

While cautioning the talks would take time, the official said Washington does not want them to run beyond a six-month deadline agreed in the November 24 deal. The late July deadline can be extended for another half year by mutual consent.

"Our intent is to use these six months to negotiate a comprehensive agreement," the official said, according to Reuters.

"I think we will certainly know in six months, in probably much sooner than that, whether the odds have increased or not to get a comprehensive agreement," the official said.

"But our goal, our objective, is to use these six months ... to get a comprehensive agreement."

Earlier Monday, Iranian Supreme Leader Ayatollah Ali Khamenei said that he had agreed to the talks with the P5+1 at the behest of some Iranian leaders, but accused Washington of using the nuclear issue as an excuse to pressure Tehran.

"The nuclear issue is an excuse," Khamenei said in a speech broadcast on state TV. "Even if one day, against all the odds, it is solved based on the Americans' expectations, then Americans will seek another issue to follow it. Just pay attention to the spokespersons of the U.S. government, who have also raised the issue of human rights, missiles and arms," said Khamenei.

Iran continued to present technological achievements in the field of military industry this week. The Commander of the country's Air Defense Forces, Farzad Ismail, said that the missile "Bawer " (Faith) made ​​in Iran, has reached the operational phase of development and that it features more advanced capabilities than the S-300 Russian-made missile system.