Blast Near U.S. Embassy Vehicle Kills 3

Military guards stand near where the bomb exploded. One American, a private citizen teaching in Beirut, was among the 20 people reported wounded. (By Mitchell Prothero -- Bloomberg News)

Lebanon has had at least 21 bombings in the past three years. The other bombs have killed politicians, journalists and a Lebanese army general, as well as bystanders. Many of those targeted were critics of neighboring Syria, which maintained troops in Lebanon until 2005 and has long sought to control Lebanese affairs.

Lebanon today is in a state of political stagnation, with no president since Nov. 24. Factional rivalries have blocked efforts to choose a successor, who must be elected by parliament.

The Lebanese army last summer defeated a militant group inspired by al-Qaeda that had taken root in a Palestinian refugee camp in northern Lebanon.

The United States has no shortage of other enemies in the region, however. The Bush administration has hostile relations with the armed Hezbollah movement, which controls much of Lebanon's south, and with Syria. The bombing occurred hours before a going-away event scheduled at a luxury Beirut hotel for Feltman, the ambassador. U.S. officials canceled the event.

Some Lebanese linked the attack to Wednesday's visit by Arab League Secretary General Amr Moussa, who will attempt to drive forward resolution of the country's crisis.

"This is the first time in 20 years that diplomatic missions are being targeted in Lebanon, and it is clear that this is an attempt to sabotage all the international efforts to solve the Lebanese crisis," cabinet member Ahmad Fatfat said.

The last attack targeting U.S. interests here was a 1991 bombing on the campus of the American University in Beirut.

Lebanon's 15-year civil war, which ended in 1990, involved frequent attacks on U.S. targets.

A 1983 truck bombing killed 241 American service members at the U.S. Marine barracks at the Beirut airport. The same year, a suicide bomber hit the U.S. Embassy there, killing at least 17 Americans, including top CIA officials.

"Above all, the message is being sent to the Americans. It is challenging them," Lebanese columnist Sarkis Naoum said.

Knickmeyer reported from Cairo. Staff writer Robin Wright in Washington contributed to this report.