Despite seven months of daily violations by both sides, the ceasefire in Gaza is holding, Mladenov said at a press conference.
Conditions remain difficult and miserable for the people of Gaza, he said.
Mladenov said the lack of progress on the peace plan underlying the ceasefire is due to the difficult issue of Hamas's disarmament.
He said the stalemate persists because Hamas has refused to give up its weapons arsenal as long as Israeli forces do not withdraw.
He also criticized Hamas for consolidating its power in areas it controls.
Around 850 people have been killed in Gaza since the ceasefire came into effect in October, according to Hamas-controlled authorities.
