The UN requires that Hezbollah and the Israeli army are notified of the route and time frame for each convoy, and for this information to be acknowledged by the two sides.
"We did not get the necessary concurrence, so we're not going," Berthiaume told The Associated Press.
Berthiaume said at least a dozen trucks with aid from WFP and other UN agencies were stuck in Beirut as a result. She would not specify whether Israel or Hizbullah, or both, was responsible for the delay.
Naqoura, close to the Israeli border, is the home of the United Nations peacekeeping force in Lebanon, while Rmaich was the scene of an Israeli shell strike on an evacuation convoy last Friday, in which a driver and a journalist were lightly wounded.
Berthiaume said that two other aid shipments carrying food, water and medical supplies from Beirut to displaced people in the north and to the southern town of Tibnine were on their way as planned.