United Nations special envoy Terje Roed-Larsen says Israel's raid into Lebanon's Bekka Valley and its ongoing blockade of Lebanon are "unhelpful" in ensuring the ceasefire.
Roed-Larsen said Sunday the truce is very fragile and can easily tilt out of control back into violence and bloodshed.
Roed-Larsen was in Beirut Sunday and later planned to head to Israel.
Israel says its raid into eastern Lebanon's Bekka Valley Saturday was a defensive move aimed at stopping Hezbollah from re-arming. Israel says it did not violate the ceasefire.
U.N. Secretary General Kofi Annan disagrees and says the action endangers what he calls the fragile calm and undermines Lebanese authority.
Israel says its blockade of Lebanon is also meant to stop weapons from reaching Hezbollah.
Meanwhile, Lebanese Defense Minister Elias Murr said Sunday that anyone firing rockets into Israel from Lebanon would be considered a traitor and dealt with harshly.
He said such an attack would give Israel reason to strike back at Lebanon.