At the end of a two-day annual summit, the Gulf Cooperation Council (GCC) rulers said they "support a political settlement... that guarantees the territorial integrity and independence of Syria."
The GCC represents the oil and gas-rich states of Bahrain, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates.
Their announcement came as Syrian opposition and armed groups met elsewhere in Riyadh in an attempt to form a unified front ahead of possible talks with the regime of President Bashar al-Assad.
Signup to our newsletter and follow us on Facebook and Twitter!
The meeting follows an agreement last month in Vienna between diplomats from 17 countries, including Saudi Arabia, for a political transition and end to the Syrian war.
The GCC "welcomed the conclusions of the Vienna meetings," the Gulf statement said.
The Vienna plan set a January 1 target for peace talks and would see a transitional government set up in six months and elections in 18 months.
Since 2011 more than 250,000 people have been killed in Syria and millions of others forced into exile.