BEIRUT -- The United Nations set up a tribunal to try suspects in the 2005 killing of former Lebanese prime minister Rafiq al-Hariri in an effort to deter future violence in Lebanon. But many in the country now fear indictments in the case could trigger a new political crisis or even sectarian bloodshed.

The Lebanese Shiite political party and militia, Hezbollah, is attempting to discredit the U.N. process amid indications that some of its members will be accused of Hariri's killing in the indictments, expected as soon as next month.

Hezbollah's leaders have pressured the Lebanese government to end its cooperation with U.N. investigators and have threatened consequences if it doesn't. Walid Jumblatt, the Lebanese Druze leader, said naming Hezbollah in the indictments would be enough to trigger a civil war like the one from 1975 to 1990.

Traditional power brokers in Lebanon, including Saudi Arabia's King Abdullah and Syrian President Bashar al-Assad, have flocked to Beirut in recent weeks to try to avert a crisis. Lebanese sources said Abdullah, who was personally close to Hariri, was so concerned about Hezbollah's warnings that he is working to delay the release of the indictments, setting up a choice for the international community between stability in Lebanon and justice for Hariri.

This internal struggle comes at a time of heightened tensions in the region and concerns about a possible war between Israel and Lebanon following a clash along their border last week that left two Lebanese soldiers, a Lebanese reporter and an Israeli military officer dead.

On Monday night, Hezbollah leader Hasan Nasrallah sought to incriminate Israel in the Hariri assassination. In an elaborate two-hour live presentation broadcast from his hiding place, Nasrallah, in a lawyer's style, tried to build a case showing how Israel could have been behind Hariri's assassination.

With dramatic flair, Nasrallah spliced his argument with video clips of Lebanese spies confessing they had worked for Israel. He questioned why the tribunal, set up two years after the killing, had not questioned any of them.

Nasrallah also showed what he claimed was intercepted Israeli surveillance footage from an unmanned aerial vehicle of Hariri's travel routes. "We think that these videos were made in preparation for an operation," Nasrallah said. He also claimed that Israeli warplanes flew over the site where Hariri's convoy was attacked on the day of the assassination and that an Israeli spy was present at the Hariri crime scene.

Nasrallah argued that Israel would have been motivated to assassinate Hariri and blame Hezbollah for the operation because Israel aims to harm the group. He said Hezbollah did not trust the U.N. investigators and would not share its findings with them.

Lebanon's prime minister, Hariri's 40-year-old son, Saad Hariri, now faces the painful choice of whether to continue to try to find out who killed his father or to acquiesce to Hezbollah in order to maintain Lebanese unity and stability, many observers said.

"He is in a tough spot," said a person close to Hariri, speaking on the condition of anonymity because of the issue's sensitivity. "But he is still committed to the tribunal. He doesn't believe Hezbollah will be able to stop it. . . . He will not allow a civil war."

Hariri, in a July 24 address to supporters, said his father's "blessed soul will not be a reason to renew civil strife in Lebanon." But he has not said how he will accomplish that. During recent past challenges, Hariri has proved incapable of withstanding pressure from Hezbollah.