Syria's rebel leader has threatened to resume attacks because president Bashar Assad's government has not honoured a ceasefire, a pan-Arab newspaper reported.
Free Syrian Army chief Riad al-Asaad told the London-based Asharq al-Awsat newspaper that "our people are demanding that we defend them".
The comments could deal yet another blow to a peace plan brokered by United Nations special envoy Kofi Annan.
Both sides of the conflict are accused of violating the ceasefire at the centrepiece of Mr Annan's plan.
On Tuesday, Mr Annan gave a bleak assessment of the crisis in Syria, saying violence remains at "unacceptable levels" and warning that his peace plan is the country's last chance to avert a disastrous civil war.
Meanwhile, an explosion targeted a Syrian military truck just seconds after a team of UN observers passed by.
An Associated Press reporter who was travelling in the UN convoy said three bloodied Syrian soldiers were rushed from the scene after the blast. The military truck had its windows blown out.
The UN convoy was not hit.
The head of the UN observer mission, Major General Robert Mood, was in the convoy.