The comments from Norwegian General Robert Mood came after NATO chief Anders Fogh Rasmussen ruled out Western military intervention and called for a political solution to the two-year-old crisis which has claimed an estimated 70,000 lives.
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"I have come to the conclusion there has to be a leveling on the playing field," Mood, who headed the UN mission in Syria until last July, told Britain's BBC TV.
"To level the playing field now in the military terms would be to consider no-fly zones, to consider whether the Patriots in Turkey could have a role also in taking on some responsibility for the northern part of Syria."
Three NATO countries - the United States, the Netherlands and Germany - sent Patriot surface-to-air missiles to Turkey early this year to protect Turkish cities from possible attack from Syria.
Six missile batteries have been stationed around three Turkish cities but are too far away in their current positions to provide an effective shield for northern Syria, according to NATO.
Mood said he did not agree with arming the rebels.
"As a principle point of view, I do believe that more weapons is not going to bring less suffering to the women and children in the neighborhoods of Damascus and in Aleppo and in the other cities in Syria," he said.
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