The mood is gruff and the talk shrill across the Middle East as growing strategic differences between Saudi Arabia and Syria underscore Iran's ability to exploit the region's fragile alliances.

Iran's backing of Hezbollah in Lebanon and Hamas in the Gaza Strip, along with its nuclear program, volatile hard-line president and support of a conservative Shiite-controlled Iraq, have unnerved Middle East politics. The atmosphere has been further agitated by Syria's growing bond with Iran, which has incensed Saudi Arabia and other Sunni Arab nations.

Iran and Syria have similar interests in keeping the atmosphere on edge, especially in Lebanon, where the Sept. 25 presidential election is a backdrop for wider regional ambitions. Iran hopes that Lebanon's Hezbollah opposition can establish a Shiite government in the midst of the Sunni world, and Syria, fearful of losing stature among its neighbors, is desperate to keep a hand in Beirut's affairs.

"The real challenge is that the bloc of moderate governments in the Middle East lacks credible leadership to counter the radical states Iran is attempting to consolidate," said Gamal Abdel Gawad, an analyst with the Al Ahram Center for Political and Strategic Studies in Cairo. "Saudi Arabia tried to act as a unifying Arab voice, but it overestimated its ability. There are limits to what checkbook diplomacy can do."

Insults swapped last month between Syria and Saudi Arabia are the most recent bitterness inflaming the Arab media. It began when Damascus said Riyadh's unsuccessful attempts to mediate the unrest in the Palestinian territories have shown that the Saudi regime is "semi-paralyzed."

The Saudis were outraged and accused Syria and Iran of provocation across the Middle East. "The problem is not in the positions of the kingdom, but in the positions of those who broke with Arab ranks and those responsible for spreading chaos in the region," a Saudi government statement said.

Syrian Foreign Minister Walid Moallem is expected to meet with Saudi officials today to calm matters. But the underlying sentiments characterize a Middle East that is at once petty and increasingly dangerous. The unpredictability of Lebanon, the war in Iraq and the political victories of Hezbollah and Hamas have underscored Syria's break with its Arab neighbors and the centuries-old Shiite-Sunni divide. Highlighting both the seriousness of the day and the region's squabbles was an earlier Saudi boycott of a conference on Iraq sponsored by Syria.

"The idea that there is a coherent Arab or Muslim voice has always been a bit of a myth," said Arshin Adib-Moghaddam, an Iranian political analyst at the University of London.

It seemed at times over the last year that Saudi Arabia, a U.S. ally, was emerging as the regional leader. It grew more engaged in Iraq, helped broker a deal between Palestinian enemies Hamas and Fatah to form a unity government, and supported Lebanese Prime Minister Fouad Siniora's besieged government, criticizing Hezbollah for the 2006 war with Israel. It was that condemnation of Hezbollah that prompted Syria to refer to Arab leaders as "half-men."

But the Palestinian pact didn't hold and Saudi Arabia's actions in Beirut angered Syria, which has felt marginalized since its troops were forced to withdraw from Lebanon in 2005 after the assassination of former Prime Minister Rafik Hariri. A United Nations investigation has tentatively linked Syrian officials to the killing, but Damascus denies any role.

Syria's animosity with Saudi Arabia, along with its determination to manipulate Lebanese affairs, has pushed it closer to Iran. Damascus went against its Arab neighbors by siding with Iran during the 1980-88 Iran-Iraq war, but the current ill will helps Iran undercut U.S. efforts to stabilize Lebanon and end sectarian fighting in Iraq, according to analysts.

"Syria has reached a decisive moment in its regional politics," said Joshua Landis, co-director of the Center of Peace Studies at the University of Oklahoma. "As it becomes clear that the U.S. must begin withdrawing from Iraq . . . Syria must decide what policy it will pursue toward a post-American Iraq. Will it side with Iran in supporting a Shiite government or will it side with Saudi Arabia in supporting the Sunni opposition?"

Syria's more immediate concern, however, is Lebanon and how Saudi and Iranian influences will affect Beirut politics.

"If Iran and Saudi Arabia reach an agreement, Syria will have very few options for sabotaging peace in Lebanon," said Hilal Khashan, chairman of political science at the American University in Beirut. "As long as the next Lebanese president is not anti-Syrian, Syria will have to heed Iranian requests for self-control in Lebanon."

There has long been "conflict between Saudi and Syrian interests, especially as far as Lebanon is concerned," said Turki Hamad, a Saudi columnist and political analyst. "However, as we are getting closer to the Lebanese presidential elections, this conflict has reached its peak."

What Syria lacks, according to many analysts, is savvy leadership in precarious times. President Bashar Assad is widely regarded as a less skilled diplomat than his late father, Hafez, who mastered regional dynamics. In addition, leaders of other Arab nations, such as Egyptian President Hosni Mubarak, have grown less influential, especially since the rise in terrorism and the Iraq conflict have jolted the Middle East.

"Hafez Assad succeeded in navigating the turbulence of inter-Arab relations. Bashar does not have the wit and intellect of his father," Khashan said. "To be honest, the challenges are graver now, and the quality of leadership is inferior."

Iran's aim is to capitalize on this by building an "axis that spreads from Tehran through Baghdad to Damascus and southern Lebanon and finally to Hamas in Palestine," Sultan Hattab, a Jordanian political commentator, recently wrote in the Arab press. "This recalls the 'Shiite Crescent' which began to crystallize after the damage done to the credibility of U.S. occupation in Iraq."

An Iranian newspaper editor, who asked not to be named for fear of arrest, said Tehran was pressuring its media not to fully report on the rift between Saudi Arabia and Syria.

"We have been told by the security guys not to write anything about the war of words between Saudi Arabia and Syria," said the editor. "That is why we detoxify the translated [newspaper] articles so that Iran seems not too much involved in the war of words."