The new U.N. envoy for Libya says members of the country's two rival parliaments have agreed to set a target date of Dec. 16 to sign a U.N.-sponsored agreement on forming a national unity government.

Martin Kobler told the U.N. Security Council in a video briefing from the Tunisian capital that some 40 lawmakers agreed at a two-day meeting in Tunis that ended Friday that the text will not be reopened.

The internationally recognized government has rejected the power-sharing agreement and the Islamist government has also expressed unhappiness with the deal.

Kobler said Libya's "social fabric, national unity and territorial integrity is directly endangered by the forces of extremism and terrorism," stressing that the Islamic State group is actively seeking to extend its influence beyond areas it now controls.