Lebanon marked Tuesday's seventh anniversary of the assassination of Rafik Hariri as a ground-breaking international tribunal investigating his death threatens to reignite the country's smoldering sectarian divisions.

Indeed, the tribunal has become highly politicized and sits at the center of what some observers call "a ticking time bomb" amid the political upheaval convulsing the Arab world, in particular the revolution in neighboring Syria aimed at bringing down the Damascus regime that so covets Lebanon.

The tribunal, mandated by the United Nations, has little to show for a seven-year effort to bring Hariri's killers to justice and the sectarian tensions surrounding its mission have risen accordingly.

The assassination of Hariri and 22 other people in a massive suicide bombing in central Beirut was, even by the murderous standards of the Middle East, a landmark event.

The tribunal indicted four members of the Iranian-backed Hezbollah organization in June . But the powerful Shiite group denies any role in killing Hariri, a member of the rival Sunni sect, on Feb. 14, 2005, with a 2.5-ton bomb.

Hezbollah leader Hassan Nasrallah refuses to hand over the suspects, who include two senior military chiefs, and he's vowed to "cut off the hands" of anyone seeking to apprehend them.

Heightening the perils ahead, sources at the tribunal, based in The Hague, say another Hezbollah member is likely to be indicted soon.

But the way things stand that suspect is as unlikely to stand in the dock as the other four. All will be tried in absentia.

If any of them are found guilty, the prospect of Hezbollah retaliating against its Lebanese rivals, Israel or the United States, or all three, is high.

If the suspects are cleared, the faction of Lebanon's Sunnis headed by Saad Hariri, the slain billionaire's son and political heir, may well seek to exact revenge for the 2005 assassination.

Hezbollah has sought to buttress itself by engineering the collapse of a Western-backed government headed by Saad Hariri in January 2011, replacing it with one it controls, with a pro-Syrian Sunni tycoon as prime minister.

However, the indictments were a major setback for a movement that boasts it is the savior of the nation by driving out Israeli occupation forces in May 2000 and fighting Israel's vaunted military to standstill in a 34-day war in 2006.

Hezbollah's image as the incorruptible leader of "the resistance" against Israel has been badly dented by the indictments, which raise the specter of Shiite-Sunni rivalry.

Hezbollah claims the tribunal is politically motivated and part of an Israeli plot to undermine the movement. It even claims that Israeli intelligence doctored mobile phone records that tribunal investigators say prove Hezbollah operatives were responsible for Hariri's death.

This has been widely seen as a Hezbollah bid to discredit the prosecution's evidence, which is heavily circumstantial and hinges on telephone intercepts.

When the U.N. investigation into the assassination was launched, Syria was the prime suspect. The outcry was such that Syria was forced to end its 29-year quasi-occupation of Lebanon.

The Americans and French, along with the Sunni monarchies of the Persian Gulf, were key backers of the investigation. It was seen by some as an opportunity to hammer Syrian President Bashar al-Assad, a key ally of Iran, who at that time was aiding insurgents fighting coalition forces in Iraq.

Damascus denied involvement and refused to cooperate. The initial findings by the investigators pointed to Syria's intelligence apparatus being behind the assassination of Hariri, who was campaigning to end Syrian domination of Lebanon.

However, when investigators said in 2009 the evidence pointed toward Hezbollah, it was viewed as an opportunity to demonize Hezbollah.

Until al-Qaida came along, Hezbollah had killed more Americans than any other militant group.

Suspicions still linger that Syria was involved since Hezbollah was its key ally and would have been unlikely to carry out an assassination of that magnitude without approval -- or orders -- from Damascus.

Hezbollah has tried to derail the tribunal and failed. Its position has been weakened by its support for Assad since the uprising to topple the Damascus regime erupted last March.

If Assad falls, as others have done, Hezbollah would lose a powerful patron and would be cut off from Iran and its main source of weapons.