The top US diplomat, who landed in the Red Sea city of Jeddah in the afternoon, also met Saudi King Abdullah a day after hosting urgent talks in Paris with the Saudi, Jordanian and UAE foreign ministers on the widening crisis in Iraq and Syria.
King Abdullah has consistently called for greater US military support for the Syrian rebels, whom the Sunni Gulf kingdom has long backed.
The request is part of a 1.5-billion USD Regional Stabilisation Initiative to bolster stability in Syrian neighbours Iraq, Jordan, Lebanon and Turkey, and to support communities hosting refugees.
Ahmad Jarba, leader of the Syrian National Coalition, welcomed the huge US boost to his forces, battling to oust Syrian President Bashar al-Assad.
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"The situation is very grave and there are sectarian leaders ruling the country so we have to have greater efforts on the part of the US and regional powers to address the situation in Iraq," Jarba said.
The Saudi king has also been an outspoken critic of Iraqi Prime Minister Nuri al-Maliki, whose Shiite-led government has seen Sunni insurgents sweep up a huge swathe of territory, including second city Mosul, since June 9.