President Bush strongly condemned the assassination of a Lebanese leader Tuesday as the work of "the vicious face of those who oppose freedom," and called it an effort to destabilize the democratically elected government of Prime Minister Fuad Saniora.

From Washington, the State Department called the murder of Lebanese Christian leader Pierre Gemayel, a foe of Syrian involvement in the country, an act of terrorism and intimidation.

While stopping short of directly blaming Syria and Iran for the assassination, Bush and other U.S. officials clearly suggested that those two countries' fingerprints are on the killing.

"We support the Saniora government and its democracy, and we support the Lebanese people's desire to live in peace. And we support their efforts to defend their democracy against attempts by Syria, Iran and allies, to foment instability and violence in that important country," Bush said after having breakfast with U.S. troops in Hawaii.

The president, visiting troops on his way home from an eight-day trip to Southeast Asia that included stops in Indonesia, Vietnam and Singapore, called for a "full investigation of the murder to identify those people and those forces behind the killing."

The U.N. Security Council unequivocally condemed Tuesday's assassination of Gemayel and approved a U.N.-Lebanese agreement that would create a tribunal to prosecute the suspected killers of another Lebanese politician — former Prime Minister Rafik Hariri.

A statement read by the council president condemned "any attempt to destabilize Lebanon through political assassination or other terrorist acts" and expressed grave concern at the possible impact of the killing of Christian politician Pierre Gemayel on efforts "to solidify democracy" in the country.

The council called Gemayel "a patriot who was a symbol of freedom and of the political independence of Lebanon."

Gemayel's assassination is expected to escalate an already tense political situation in Lebanon and came hours before a deadline for Security Council members to approve a letter authorizing Secretary-General Kofi Annan to conclude the agreement with the Lebanese government to establish the mixed tribunal.

The deadline for objections was 6 p.m. EST on Tuesday, but the U.S., French and Qatar ambassadors announced after closed consultations that the letter had been approved by all 15 council members almost two hours early.

"I strongly believe that the United Nations Security Council ought to act today," Bush said. "For the sake of peace, the free world must reject those who undermine young democracies and murder in the name of their hateful ideology."

Referring to the investigation into the assassination of Hariri, who also tried to limit Syrian influence in the country, Bolton told reporters: "I think people can draw their own conclusions" about the Gemayel killing.

Asked whether the U.N. Security Council should continue with the Hariri tribunal because of the "instability" now in Lebanon, U.N. ambassador John Bolton lashed out.

"How incredibly wrong that would be. How incredibly wrong that would be. Instability? They're killing people in Lebanon. They're assassinating political leaders. Not the time to seek justice? There may be those on the Security Council who say it. Let them step forward and say it," Bolton said.

Undersecretary of State Nicholas Burns told reporters the administration was shocked by the assassination.

"We view it as an act of terrorism," he said. "We also view it as an act of intimidation."

Burns took note of recent statements by Hezbollah leader Sheik Hassan Nasrallah and others that he said are meant "to destabilize Lebanon and to divide the country."

Nasrallah has urged his followers to prepare for mass demonstrations to topple the U.S.-supported government headed by Saniora if it ignores the group's demands to form a national unity Cabinet. Hezbollah, an ally of Syria and U.S.-designated terrorist organization, gained political strength in the country as a result of the war it fought in July and August against Israel.

The United States has accused Syria and Iran of plotting to topple Saniora's government, which is dominated by politicians opposed to Syrian influence in Lebanon.

Secretary of State Condoleezza Rice telephoned Saniora with condolences and to reiterate U.S. support for democracy in Lebanon, Tom Casey, a State Department spokesman, said.

Burns praised Saniora's 20-month old government, seeing it as a step toward returning Lebanon "to a position of real sovereignty, freeing it from Syria's influence and from "the politics of violence and assassination."

"We believe it is the responsibility of all countries to support the Saniora government," he said. "We will give full support to the Saniora government in the days and weeks ahead."

In brief remarks about the assassination at the Pentagon, Defense Secretary Donald H. Rumsfeld said, "It is certainly a tragedy for Lebanon and for those in Lebanon and that part of the world that believe in peace and representative systems."

The Associated Press contributed to this report.