Iranian President Hassan Rouhani on Monday called for a united front to fight extremists in the Middle East and said Tehran was ready to help "bring about democracy" in Syria and Yemen.

Making his first address to the U.N. General Assembly since the historic nuclear deal was reached, Rouhani waded into the intense diplomatic debate over fighting jihadists and pushing for regime change in Syria.

U.S. President Barack Obama on Monday took a swipe at Russia and Iran for backing what he called "tyrants" like Syria's Bashar Assad but declared in his address to the United Nations that he was ready to work with them to end the conflict.

Obama took the podium at the U.N. General Assembly ahead of President Vladimir Putin and Iranian leader Hassan Rouhani, with the spotlight firmly on ending the carnage in Syria.

Russia and the United States are expected to take part in Syria peace talks in October, along with Iran, Saudi Arabia, Turkey and Egypt, Russia's deputy foreign minister said Monday.

A meeting of an international contact group of the "most influential outside players" will "be pushed forward to October after the U.N. General Assembly," deputy foreign minister Mikhail Bogdanov said, quoted by RIA Novosti news agency.

President Hassan Rouhani will fly home early from New York to attend a repatriation ceremony in Tehran on Tuesday for Iranian pilgrims killed in the stampede at the hajj, his office said.

Rouhani is to head home straight after his address to the U.N. General Assembly later on Monday, the Iranian mission at the United Nations said.

Iranian President Hassan Rouhani said Sunday he saw a widespread acceptance among major powers that Syrian leader Bashar Assad should stay in office.

"I think today everyone has accepted that President Assad must remain so that we can combat the terrorists," Rouhani told CNN.

Tehran will work to free three Americans from its prisons if the United States releases jailed Iranians, President Hassan Rouhani said Sunday.

"If the Americans take the appropriate steps and set them free, certainly the right environment will be open and the right circumstances will be created for us to do everything within our power and our purview to bring about the swiftest freedom for the Americans held in Iran as well," Rouhani told CNN.

Hundreds of Iranians chanted "Death to the treacherous House of Saud" outside the Saudi embassy on Sunday as the Islamic republic's leader demanded Riyadh apologize for the deadly hajj stampede.

Iraq, Russia, Iran and Syria have agreed to set up an intelligence committee in Baghdad, a spokesman said Sunday, a further sign of Moscow's growing role in the region's conflict.

Iraq welcomed the creation of the new cell as a chance to help harmonize often competing efforts in the fight against the Islamic State (IS) jihadist group.

Loyalist forces in Yemen backed by a Saudi-led coalition killed at least 20 Iran-backed insurgents Saturday, the military said, as they pressed their offensive on the rebel-held capital Sanaa.

Twelve other rebels were captured in the operation launched on the northwestern edge of Marib province, a key battleground in the fight for control of the capital, said a military official

Pope Francis arrived in Philadelphia Saturday for the final leg of his triumphal tour of the United States, with hundreds of thousands expected to turn out for his weekend visit focused on families.

The head of the world's 1.2 billion Catholics landed in the City of Brotherly Love after a short flight from New York, where he spent a whirlwind 36 hours that included an emotional visit to Ground Zero and mass at Madison Square Garden.