As at previous summits, the leaders of the 22-member Arab League criticised Iran, but without naming the Shiite-dominated main regional rival of Sunni-ruled Saudi Arabia.
"We reject any intervention in the internal affairs of Arab countries," they said in a declaration at the end of their one-day meeting in the Jordanian town of Sweimeh on the Dead Sea coast.
In their statement, they also called for a revival of "serious and productive peace negotiations between Israelis and Palestinians" and renewed their commitment to a two-state solution.
Palestinian president Mahmud Abbas told the leaders he would refuse to accept "temporary or regional" attempts to solve the conflict.
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Abbas, who met yesterday on the sidelines of the summit with Trump adviser Jason Greenblatt, is expected to visit the White House next month.
Arab League head Ahmed Abul Gheit told the summit he regretted the fact that member states were watching "events in Syria without the possibility of intervening," calling the conflict "shameful".
"We will not allow any power to intervene in our affairs," said Sisi. "And any attempt at confessional or territorial domination... Will have to face a clear and firm Arab position."
Iran is also accused of supporting Shiite Huthi rebels fighting government forces who have been backed by a Saudi-led Arab military coalition since 2015.
Arab leaders have been unable to find common ground on how to end Syria's conflict, which in six years has killed more than 320,000 people and forced millions from their homes.
While some say Assad must stand down in any peace deal, others, including Sisi, have not insisted on his departure as a condition for a political agreement.
The divisions have allowed other nations including Iran, Russia and Turkey to take the initiative.