Kerry arrived in Riyadh late on Wednesday from Montreux, Switzerland, where he said he had made progress in talks with Iranian Foreign Minister Mohammad Javad Zarif that aim to conclude an atomic deal by the end of March.

Gulf countries, like Israel and many Western states, fear that Iran is using its atomic programme to develop nuclear weapons capability, something Tehran denies.

Israeli Prime Minister Benjamin Netanyahu told the US Congress this week that the deal being negotiated by Washington and other world powers was a serious mistake.

Although they did not publicly endorse his comments, Saudi Arabia and some other Gulf Arab states share his concern that the mooted accord would not be strong enough to stop Iran from gaining the bomb, or that it would lift international pressure on Tehran and give it more room to intervene in regional issues.

Sunni Muslim Saudi Arabia regards Shi'ite Iran as its main regional rival and the two countries back opposing sides in wars and political struggles in Syria, Iraq, Bahrain, Lebanon and Yemen, often along sectarian lines.

Kerry was scheduled to meet King Salman and Deputy Crown Prince Mohammed bin Nayef, who is also Interior Minister, after his meeting with foreign ministers of the six members of the Gulf Cooperation Council.

The GCC includes Saudi Arabia, Kuwait, Bahrain, Qatar, the United Arab Emirates and Oman.

Kerry also held a separate meeting at the start of the day with Oman's Foreign Minister Yusef bin Alawi bin Abdullah. Muscat helped facilitate months of secret talks between Iran and the United States in 2013 that led to the push for a deal.