Beirut ? The leaders of Syria and Saudi Arabia, once bitter rivals, made an unprecedented show of cooperation Friday, traveling together to Lebanon in hopes of preventing any violence if members of a militant group are indicted in the 2005 assassination of a former Lebanese prime minister.

The unusual joint visit by Syrian President Bashar Assad and Saudi King Abdullah underscored the depth of Arab concern over potential chaos in Lebanon. Many people fear indictments of Hezbollah members could spark clashes between Lebanon’s Sunnis and Shiites, or that Hezbollah’s nemesis Israel could be pulled into a conflict, causing wider turmoil.

The summit also consecrated both countries’ roles as power brokers in the region, where Syria is an ally of Iran and Saudi Arabia generally supports the U.S.

Washington has long tried to uproot Syrian influence in Lebanon, but Damascus and Riyadh seem to have a fragile understanding, suggesting both see a greater interest in keeping Lebanon quiet after years of feuding over it.

“This is significant for two leaders who were fighting it out in Beirut just a few years ago,” said Paul Salem, director of the Carnegie Middle East Center in Beirut. “This indicates that they think this crisis is so big that they have to come themselves.”