Lebanon's democratic government apparently cannot convene a promised tribunal to deal with the assassination of a leading politician, and the United States may ask the United Nations Security Council to step in, US officials said Friday. The State Department's top Middle East diplomat suggested that the US-backed government in Beirut is partly to blame for a political impasse over the international tribunal. "It appears that because of interference from the outside, indecision inside and opposition inside, that Lebanon's normal constitutional processes cannot address this matter," Assistant Secretary of State David Welch said. The panel to prosecute suspects in the 2005 assassination of former Prime Minister Rafik Hariri was meant to clear the air in Lebanon's fractured and suspicious political culture. Instead, it has become a defining symbol for the country's difficulties. Prime Minister Fuad Saniora's weak government has demanded the tribunal be created, but the opposition parliament speaker, Nabih Berri, has not convened the legislature to approve the court. The deadlock threatens Saniora's government. Although Saniora is admired for standing up to pro-Syrian forces and the political and militia group Hizbullah, Western diplomats have expressed disappointment that he has not resolved the crisis. The United States and other members of the UN Security Council would prefer that Lebanon run the tribunal under its own laws, but several diplomats have said the council could establish its own independent panel if necessary. "If it's not possible to do this through Lebanon's normal constitutional processes, then the United States and others will find another way to do it," Welch told reporters at a State Department briefing. The struggle over the tribunal has included sit-ins, street clashes and killings that led many to fear that the country was returning to the violence of the 1975-90 civil war. The Hizbullah-led opposition has led protests outside the prime minister's office, trying to force him to resign or to share power in a coalition that would give the opposition veto power. Lebanon's anti-Syrian faction blames Damascus for the massive truck bombing that killed Hariri and 22 others and claims the Syrians are using their Lebanese allies, including Hizbullah, to undermine formation of the tribunal. Syria denies the accusations. US officials, said the United States, probably with France, could sponsor a new mandatory Security Council resolution to set up a tribunal patterned on previous prosecuting panels for the former Yugoslavia, Rwanda, Sierra Leone and Cambodia. The United Nations and the Lebanese government agreed last year on terms of the tribunal, and the UN version probably would use the same guidelines, said US officials who spoke on condition of anonymity because the process is preliminary. The UN legal chief was in Beirut this week to prod the feuding leaders to ratify the tribunal, warning that their agreement is necessary to avert possible UN Security Council intervention. Nicolas Michel, the UN undersecretary-general for legal affairs who helped draft the treaty on the tribunal, is expected to brief the Security Council as early as next week. The United States will wait for that discussion before deciding what to do next. The Bush administration has pointed to Lebanon as perhaps the best example of democratic change in the Middle East. The killing of Hariri, who had tried to peel his country away from decades of Syrian domination, emboldened anti-Syrian forces. Massive street demonstrations and international pressure eventually forced Syria to withdraw forces from Lebanon, and helped propel Saniora to power.