His talks, scheduled for later in Riyadh, come a day after the top US diplomat vowed United States would stand by its friends as they navigate the turmoil unleashed by the Arab Spring.

The political upheaval sweeping parts of the Middle East has witnessed the rise of powerful new extremist groups in Libya and Syria, with Iran accused of fomenting unrest to aid Syrian President Bashar al-Assad in his 31-month battle against rebel forces.

Saudi Arabia, locked in a decades-long rivalry with Iran, is concerned that proposed Syrian peace talks could leave a Tehran-backed regime in Damascus and that a breakthrough in nuclear negotiations could also lead to a US rapprochement with its arch foe.

"We will be there for Saudi Arabia, for the Emirates, for Qataris, for the Jordanians, for the Egyptians and others. We will not allow those countries to be attacked from outside. We will stand with them," Kerry told reporters on Sunday, during a brief visit to Cairo.

His comments came at the start of an 11-day trip which has become an exercise in damage control, as the regional turbulence unleashed by the Arab Spring stirs tensions with longtime US partners. Saudi Arabia has grown increasingly nervous as popular revolts have toppled onetime allies in Egypt, Tunisia and Yemen.

In an unprecedented move in October 2013, the conservative oil-rich kingdom turned down a coveted non-permanent seat on the UN Security Council in protest at the world body's failure to end the war in Syria, which has killed more than 120,000 people.

In Cairo, Kerry acknowledged that while there might be differences over "tactics" in ending the Syrian conflict, the goal for the United States and its allies was the same, a transition of power. The US has been pressing Syria's opposition to attend the Geneva peace talks with the Assad regime, slated for late November.

And it won the support of the Arab League, which meeting late on Sunday in Cairo said it would "encourage" the Syrian opposition to attend the talks aimed at ushering in a transitional government.

Syria's opposition has refused to attend unless Assad's resignation is on the table, a demand Damascus rejects.

(Agencies)

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