President Bush said he is disturbed by published reports that Syrian intelligence agents are still in Lebanon, and he called on Damascus to follow up on the allegations.
Earlier White House spokesman Scott McClellan accused Syrian intelligence agents in Lebanon of meddling in the country during its ongoing national elections.
Damascus said it withdrew its troops and agents from Lebanon in April, amid intense pressure following the murder of former Lebanese prime minister Rafik Hariri.
The White House says it supports a U.N. plan to send a team to Lebanon to verify that Syrian agents have left.
U.S. news reports published today quoted U.S. officials as saying Syria may be targeting key Lebanese leaders for assassination.
Prominent Lebanese politician Walid Jumblatt also accused Syrian agents of targeting opposition leaders.