Libya's rival parliaments are to resume UN-brokered talks in Morocco on Thursday on forging a united administration for the divided and violence-wracked country, a diplomatic source told AFP.

That is a day later than planned by the United Nations and comes despite a statement adopted unanimously by the Security Council late on Monday saying that it awaited the resumption of the talks "with impatience".

Libya has had rival administrations as well as parliaments since an Islamist-backed militia alliance seized the capital in August prompting the internationally recognised government to take refuge in the east.

The resulting power struggle has been exploited by the Islamic State jihadist group to establish a growing presence to the alarm of the international community.

The Tripoli parliament -- the General National Congress -- confirmed that it would attend the talks in Skhirat outside Rabat.

"Our delegation will arrive on Wednesday to start a new round of negotiations," GNC member Mohammed Saleh al-Makhzum told AFP.

The UN Security Council called on the rival sides to "agree on arrangements on the formation of a national unity government to end Libya's political, security and institutional crisis."

The council also warned it was "prepared to sanction those who threaten Libya's peace, stability or security or that obstruct or undermine the successful completion of its political transition."