Time is running short to reach a nuclear deal between world powers and Iran, and negotiations will not be extended merely as a foot-dragging ploy, top U.S. diplomat John Kerry warned Tuesday.

On the eve of the most intensive round of talks yet, Kerry called on Iran to make the right choices and prove to the world its claims that its nuclear energy program is peaceful by closing what he called "substantial gaps" in the negotiations.

Newly-appointed Iranian Ambassador to Lebanon Mohammed Fathali reiterated on Tuesday that his country is ready to provide Lebanese security agencies with all the necessary aid, stressing that the Lebanese presidential poll is a local affair.

“We have announced since day one that we are ready to cooperate with the Lebanese army and all security agencies on high levels,” Fathali said in an interview with As Safir newspaper.

Iran's supreme leader Ayatollah Ali Khamenei has warned against any bid to end the house arrest of two top opposition leaders, a champion of their release told Iranian media Monday.

Lawmaker Ali Motahari, a supporter of President Hassan Rouhani, said Khamenei had told him the house arrest imposed on the two defeated 2009 presidential election candidates was a "favor" and that they would face far worse punishment if they stood trial.

The leaders of Shiite Iran and Sunni Qatar vowed Sunday to cooperate to fight "terrorism in the region," President Hassan Rouhani's office reported as Iraqi forces counter a militant onslaught.

The pledge to play a "constructive role to establish security and stability" came in a phone call between Qatari Emir Sheikh Tamim bin Hamad al-Thani and Rouhani, a statement from the Iranian president's office said.

World powers reaffirmed their commitment Thursday to reaching agreement with Iran on its contested nuclear program by a July 20 deadline, after Tehran lashed out at "excessive demands" made by them.

Officials from Britain, China, France, Russia and the United States -- the five permanent members of the U.N. Security Council -- plus Germany met European Union foreign affairs head Catherine Ashton for "an intense day of preparation" for talks next week with Iran.

Iran has offered "rational proposals" in nuclear negotiations but "excessive demands" of the P5+1 world powers are likely to prevent agreement by the July 20 deadline, Tehran's foreign minister said Thursday.

The five permanent members of the U.N. Security Council plus Germany are trying to secure a mammoth deal by next month to reduce in scope Iran's nuclear program and ease fears the Islamic republic will get atomic weapons.

Iran is rushing to try to save one of the world's critically endangered species, the Asiatic cheetah, and bring it back from the verge of extinction in its last remaining refuge.

The Asiatic cheetah, an equally fast cousin of the African cat, once ranged from the Red Sea to India, but its numbers shrunk over the past century to the point that it is now hanging on by a thin thread — an estimated 50 to 70 animals remaining in Iran, mostly in the east of the country. That's down from as many as 400 in the 1990s, its numbers plummeting due to poaching, the hunting of its main prey — gazelles — and encroachment on its habitat.

Unidentified gunmen have killed three Iranian police on patrol in the northwest of the country near the border with Iraq, the Mehr news agency reported on Wednesday.

Tuesday night's attack comes after the authorities in Shiite-ruled Iran beefed up security along the frontier in response to a Sunni militant offensive that has captured swathes of Iraqi territory.

Speaker Nabih Berri has urged the rival Lebanese parties to unite against the dangerous security situation in Lebanon, saying they should elect a president and activate state institutions.

“The situation is very dangerous particularly after what happened in Iraq” and the freeze in the rapprochement between Iran and Saudi Arabia, local newspapers quoted Berri as saying.

Russian President Vladidmir Putin and his U.S. counterpart Barack Obama on Monday expressed "serious concern" over the advances of jihadists from the Islamic State of Iraq and the Levant (ISIL) in Iraq.

"The Russian leader expressed support for Baghdad's efforts in the fight against Islamists and bringing about peace and stability in the country," said the Kremlin statement after phone talks between to two rivals, adding the two leaders also discussed Syria and Iran's nuclear program.