Saudi Foreign Minister Prince Saud al-Faisal is due in Vienna later Sunday where U.S. Secretary of State John Kerry will update him on nuclear talks with Iran, a senior U.S. official said. 

Kerry will "meet with Saudi Foreign Minister Saud al-Faisal to update him on the (Iran) negotiations," the senior State Department official said.

World powers and Iran began discussing late Sunday whether more time is needed to reach a nuclear deal, a U.S. official said, as they struggled to overcome major gaps barely 24 hours before a deadline.

British Foreign Secretary Philip Hammond said world powers and Iran will make a "last push" for a deal before Monday's deadline even though the parties are far apart.

The upcoming weeks could be decisive in determining the election of a president given the regional and international interest to end the vacuum at the Baabda Palace, reported the pan-Arab daily Asharq al-Awsat on Sunday.

Christian sources from the March 14 camp told the daily that France, the Vatican, and Saudi Arabia are pressuring Lebanese powers to end the vacuum.

World powers and Iran have still made no real progress in negotiations over Tehran's nuclear program and it looks "physically impossible" to strike a comprehensive deal by Monday's deadline, a European source said Saturday.

The source close to the negotiations said "no significant progress" has been achieved until now and "there is even a chance that we will not" reach an agreement by Monday's deadline.

Iran's press has highlighted the high stakes and potential benefits of Tehran striking a deal with world powers over its nuclear program, as talks remain deadlocked ahead of Monday's deadline.

Kayhan, a newspaper considered close to supreme leader Ayatollah Ali Khamenei, said Saturday that President Hassan Rouhani's negotiators must deliver a complete lifting of sanctions.

Deadlocked international talks aimed at defusing a 12-year standoff with Iran over its nuclear ambitions entered their cliffhanger final weekend Saturday, days before a deadline.

In a sign of the high stakes involved, U.S. Secretary of State John Kerry and his Iranian counterpart Mohammed Javad Zarif stayed overnight Friday in the Austrian capital Vienna in a bid to break the deadlock in a year-long round of rollercoaster negotiations.

Iran has freed an Iranian-Canadian journalist dubbed "the blogfather" who was jailed for 19 years for traveling to Israel, local media reported Thursday.

Hossein Derakhshan was arrested in November 2008 after visiting Israel -- Iran's arch-foe -- with his Canadian passport on what he called a mission to breed understanding between Iranians and Israelis. 

U.S. Secretary of State John Kerry arrived in Vienna Thursday to join troubled nuclear talks four days before a deadline, with Russia warning that getting a deal will be "very difficult."

Speaking in Paris earlier, Kerry said that together with British counterpart Philip Hammond -- who Wednesday said he was "not optimistic" -- he was "concerned about the gaps."

France is seeking to encourage Iran to help the rival Lebanese politicians strike a deal on a new consensual president over fears that the regional turmoil would harm coexistence in Lebanon, diplomatic sources said.

The sources told An Nahar newspaper published on Thursday that the French initiative comes with an American support to fill the vacuum at Baabda Palace.

The Iranians conducting nuclear talks with world powers seem loath to use the word "compromise", but with much to lose President Hassan Rouhani may yet be pushing for a last-minute deal.

Negotiations to reach a final agreement on Iran's disputed atomic program -- culminating this week in Vienna ahead of a November 24 deadline -- have divided the Islamic republic.