BEIRUT – The head of the U.N. observers in Syria said Friday a spike in bloodshed is derailing the mission to monitor and defuse more than a year of violence, raising questions about how effective the unarmed force can be in a conflict that every day looks more like a civil war.

The troubles facing the observer mission are the latest sign that an international peace plan for Syria is disintegrating. Western powers have pinned their hopes on the plan, brokered two months ago by special envoy Kofi Annan, in part because there are no other options on the table. There is little support for military intervention, and several rounds of sanctions have failed to stop the bloodshed.

"Violence over the past 10 days has been intensifying willingly by the both parties, with losses on both sides and significant risks to our observers," Maj. Gen. Robert Mood told reporters in Damascus, the Syrian capital.