The United States Monday strongly condemned the assassination former Lebanese Prime Minister Rafik Hariri. U.S. spokesmen made no direct charges of blame, but said it is time for Syria to heed the U.N. Security Council resolution calling on it to withdraw from Lebanon.

Mr. Hariri, a wealthy businessman-turned-politician, was well-liked in Washington for his work to re-build the war-torn country, and for being an independent voice amid heavy Syrian influence in Lebanon.

His assassination in a car-bomb attack Monday in Beirut was condemned by the White House as a "despicable act," and an attempt to stifle efforts to build an independent, sovereign Lebanon.

White House spokesman Scott McClellan said the United States will consult with other members of the U.N. Security Council about what can be done to punish those responsible, and to restore Lebanon's independence by ending what he termed foreign occupation.

Syria sent troops into Lebanon under an Arab League mandate at the height of the country's civil war in the 1970s, and continues to have about 14,000 soldiers there despite a 1989 agreement in principle to withdraw them.

The United States, working closely with France, succeeded last September in getting a resolution approved by the U.N. Security Council calling for the withdrawal of all foreign forces from Lebanon.

In news briefings, neither Mr. McClellan nor his State Department counterpart Richard Boucher accused Syria of being behind the killing of Mr. Hariri, saying the United States does not know who was responsible.

But Mr. Boucher said it was an appropriate time to remind Syria of its obligations under Security Council resolution 1559: "The United States takes this opportunity once again to call for the immediate implementation of Resolution 15-59, including the withdrawal of all Syrian forces, the disbanding and disarmament of all militias, and an end to foreign interference in the political independence of Lebanon. The Lebanese people must be free to exercise their political choices without intimidation or the threat of violence," he said.

The assassination of Mr. Hariri comes at a tense point in U.S.-Syrian relations. The United States has accused Syria of at least tolerating the presence of members of the former Saddam Hussein regime who have been directing the Iraqi insurgency.

It has also criticized Syria for playing host to Palestinian extremist factions opposed to Middle East peace efforts, and of failing to curb the pro-Iranian Lebanese Hezbollah militia.

After initially opposing the idea, the Bush administration went along with the approval by Congress in 2003 of the Syria Accountability Act providing for U.S. sanctions against Damascus. Last May the White House imposed some of the punitive steps, including a ban on most trade with that country.

The cosponsor of the law, House Democrat Eliot Engel of New York, told reporters Monday he would not be surprised if Syria was behind the Hariri assassination, as an effort sow chaos in Lebanon and stem pressure for its withdrawal. Mr. Engel said remaining, and more serious, sanctions in the legislation should now be imposed:

"In view of what happened in Lebanon today, with the bombing and assassination of the former Prime Minister, we need to implement the entire Syria Accountability Act, and the President also has some things as his disposal that he can implement as President. And I just think that we need to tell Syria that this is unacceptable and we're going to have to do everything in our power to change their behavior, and not to tolerate this sort of thing," he said.

In a television interview, meanwhile, Syria's Ambassador to Washington, Imad Moustapha, condemned the assassination of Mr. Hariri as a dangerous threat to Lebanese unity, and rejected suggestions that the former Prime Minister was an enemy of Syria.

He also criticized the White House and State Department for tying their reaction to the killing to calls for Syria's departure from Lebanon.