The U.N. envoy to Libya is calling for a unity government as he opens meetings in Geneva with the country's warring political factions, warning they shouldn't miss the opportunity for peace.

Bernardino Leon said Wednesday the talks are the start of a long process. One of Libya's two rival parliaments won't even decide until Sunday whether to participate.

Libya has been mired in its worst fighting since Moammar Gadhafi's regime was overthrown in 2011. Two rival governments are each backed by an array of militias.

Leon said: "The general impression is that the country is very close to total chaos and that, if they miss this opportunity, it's very difficult to imagine that there will be a situation in the country that will allow easily to start a new process."