JEDDAH - Saudi Arabia on Tuesday pressed for global action to end Syrian President Bashar al-Assad's regime, telling US Secretary of State John Kerry that the civil war had turned into "genocide".

Kerry met leaders of the Arab monarchy as part of a regional tour in which he has called for greater support for Syria's rebels but stressed that the United States ultimately wanted a political solution that includes all sides.

Saudi Foreign Minister Prince Saud al-Faisal told Kerry that Assad, a secular leader who belongs to the heterodox Alawite sect, has waged "unprecedented genocide" through the more than two-year conflict that has claimed nearly 100,000 lives. "The kingdom demands a clear, unequivocal international resolution that bans any sort of weapons support for the Syrian regime and declares null and void the legitimacy of that regime," Faisal said at a joint news conference.

"The regime's illegitimacy eliminates any possibility of it being part of any arrangement or playing any role whatsoever in shaping the present and future," he said.

Faisal also voiced dismay at the role of Iran, which has poured assistance to Assad to save its main Arab ally. Hezbollah, the Lebanese Shia Muslim backed by Iran, has increasingly fought alongside government forces in Syria.

"Along with the regime's genocide against its own people, this adds an even deadlier element in the form of an all-out foreign invasion," Faisal said of Iran's role.

President Barack Obama has vowed to step up support for the rebels after concluding that Assad defied warnings and used chemical weapons. But Obama is cautious about deeper involvement in an increasingly sectarian conflict.

US policymakers have privately voiced concern that Saudi Arabia and fellow monarchy Qatar could embrace guerrillas in strategically placed Syria if Western powers leave a vacuum.

Despite Faisal's stance, Kerry said that the United States supported an agreement last year in Geneva that would create a transitional government that includes both the rebels and regime, although not Assad himself.

"We believe that the best solution is a political solution in which the people of Syria have an opportunity to be able to make a choice about their future," Kerry said.

"We believe that every minority can be respected, there can be diversity and pluralism and that the people can do so in a climate of peace," he said.

Kerry also paid his day trip to Jeddah to compare notes on the Middle East peace process - one of his key priorities - and on the chaotic politics of Egypt, where Saudi Arabia is considered to hold key influence.

Kerry voiced hope that weekend demonstrations planned against President Mohamed Mursi would be peaceful and instead encourage action by the government on measures including structural reforms to revive a moribund economy.

"We will obviously hope that it will not produce violence and be a moment of catalysing positive change in Egypt," Kerry said.

Kerry said he compared notes with Saudi Arabia on the Middle East peace process. He heads later Tuesday to Kuwait and later goes to Jordan in his latest mission to move forward on reconciliation between Israel and the Palestinians.