Lebanese Prime Minister Fuad Siniora says Lebanon will not be intimidated by the killers of anti-Syrian politician Pierre Gemayel.
Mr. Siniora spoke hours after gunmen shot and killed the industry minister in a Christian neighborhood near Beirut Tuesday.
The international community has condemned the assassination.
The European Union called on all parties to avoid actions that would destabilize Lebanon.
U.N. Secretary-General Kofi Annan praised Gemayel as someone who believed strongly in an independent, democratic and united Lebanon.
And President Bush said the United States supports the Lebanese government's efforts to defend itself against what he called attempts by Syria, Iran and allies to foment instability and violence in Lebanon. He called for a full investigation into the attack.
Syria's U.N. ambassador, Bashar al-Jaafari, said his country had no role in what he called "horrible crimes" in Lebanon.
Six pro-Syrian cabinet members recently resigned to back the Shi'ite militant group Hezbollah's demand for veto power. Hezbollah has called for an end to Mr. Siniora's government.
U.S. Under Secretary of State Nicholas Burns said the murder was an act of terrorism and intimidation against Lebanon's elected government.
The U.S. envoy to the United Nations, John Bolton, said the killing highlights the need for the quick creation of a special tribunal for Lebanon. The proposed court would try suspects in last year's assassination of former Lebanese Prime Minister Rafik Hariri.
Prime Minister Siniora said Lebanon must stand united for the creation of the international tribunal.
Several other anti-Syrian politicians have been assassinated in Lebanon in the past two years. A U.N. inquiry has implicated Syrian officials in the Hariri killing. Damascus has denied any involvement.