US Secretary of State John Kerry and Italian Foreign Minister Paolo Gentiloni were co-hosting the conference that also included representatives from 16 nations, the African Union, the Arab League and the United Nations.
After meeting by themselves in the morning, the officials brought in the Libyan sides and urged them to sign the UN deal, as they have pledged to do in Morocco on December 16.
Harlem Desir, France's secretary of state for European affairs, predicted "unanimous consensus" on the UN plan. He said UN special envoy for Libya, Martin Kobler, made assurances that the Wednesday signing will take place.
Kobler, also at the Rome meeting, had mediated the session in Tunisia at which some 40 Libyan lawmakers from the two sides agreed to sign the deal.
Libya slid into chaos following the 2011 toppling and killing of dictator Moammar Gadhafi. Since then, it has been torn between an internationally recognized government in eastern Tobruk and an Islamist-backed government in the capital, Tripoli, and now faces threats from Islamic State extremists.
Libya's oil industry has been largely crippled by the crisis. Proper management, as well as that of the central bank, is considered essential to the country's viability.
The plan would extend the reconstituted parliament's term by one year and allow for an automatic one-year extension of its mandate beyond that, if necessary.
The United Nations and many countries concerned about Libyan crisis and the rise of IS stepped up efforts to get the rival governments to accept the power-sharing agreement since the factions rejected the deal in October.
