"This needs to happen immediately," State Department spokesman Tom Casey said in response to an announcement that Syria would draw the troops back closer to its border.
A resolution by the U.N. Security Council "calls in clear, unequivocal terms for all foreign forces to withdraw from Lebanon," Casey said.
Syria's move, apparently designed to blunt that demand, will not sidetrack talks that a senior State Department official, David Satterfield, plans to hold in Lebanon early next week, the spokesman said.
Satterfield, a former U.S. ambassador to Beirut (search) and now a deputy assistant secretary of state, will convey the U.S. demand for a full and immediate withdrawal.
He also will talk to Lebanese officials about the need for a thorough inquiry into last week's assassination of former Prime Minister Rafik Hariri (search), department spokesman Richard Boucher said Wednesday.
Thursday's tough U.S. statement reflects both skepticism that Syria will comply and a downturn in relations with Syria, accelerated by Hariri's assassination.
Syria in the past has redeployed its troops in Lebanon in ways that seemed to indicate a pullout was in the works. But the troops remain in Lebanon, reinforcing Syria's dominant role in Lebanon's politics.