Conflict in neighboring Syria has threatened to spill into Lebanon. Also, anti-American sentiment in the region in general remains high as protests continue over a film produced in the United States that was deemed insulting to Islam.
Hezbollah Secretary-General Hassan Nasrallah on Sunday accused the White House of trying to stoke divisions between religious communities in the region.
"The U.S. administration says that it will do nothing (about the film), citing the idea we all know of freedom of speech and American principles," he was quoted by The Daily Star newspaper in Lebanon as saying.
Nasrallah, sanctioned last week by the U.S. government, called for more anti-American demonstrations.
The State Department travel warning noted protests in Lebanon can turn violent with little or no warning. Hezbollah, considered a terrorist organization by the U.S. government, controls parts of Beirut and southern Lebanon, the warning adds.
U.S. diplomatic outposts across the region remained on high alert. The U.S. Embassies in Azerbaijan and Indonesia warned citizens to avoid demonstrations planned Monday.