Libya's Tripoli-based General National Congress (GNC) representative Salih el-Mahzum (R) and Libya's Tobruk-based government's representative Muhammed Shuayb (L) sign the "Libyan Political Agreement" in Suheirat, Morocco December 17, 2015. [Photo/Agencies]

PRESIDENTIAL COUNCIL

Under the deal, a nine-member presidential council will form a government, with the current, eastern-based House of Representatives as the main legislature, and a State Council as a second, consultative chamber. The presidential council will name a new government in a month and a UN Security Council resolution will endorse it.

"There are some people who want to hold on to little kingdoms, but very, very small kingdoms, little tiny patches where they hold authority, but Libya's going to move on," US envoy to Libya Jonathan Winer told Reuters. "Ultimately, Libyans have to be responsible for Libya."

The US State Department said Washington was committed to providing the unified government with "full political backing and technical, economic, security and counterterrorism assistance".

Still, the agreement faces questions from critics about how representative the proposed government will be, how it will set up in Tripoli, and how various armed factions on the ground will react to a new government. Some brand it a UN-imposed deal.

Some of Libya's armed brigades have backed the deal, while others are closely allied with political leaders who oppose it.

"We have reached an agreement, but the biggest challenge now is to implement it," said Salah Huma, a member of parliament and negotiator for the eastern-based government.

The chiefs of the two rival parliaments have already rejected the UN deal and called for more time to negotiate a Libyan initiative, though diplomats say both men may face international sanctions for blocking a vote on the agreement.