U.N. Secretary-General Antonio Guterres on Saturday said he supports the African Union (AU) taking a greater role in mediating the Libya crisis, acknowledging the bloc's frustration at being sidelined so far.

The AU leadership has complained of being overlooked in peacemaking efforts related to Libya, which have been led primarily by the U.N. and heavily involved European nations.

"We want the African representatives to attend all the meetings," Guterres said, apparently in ire about the fact that involvement of Africa in the Berlin conference on Libya was minimal.

Guterres' remarks came in a news conference he held a day before the official opening of the African Union's 33rd Assembly of African Heads of State and Government.

"There are a number of players and military equipment and armies in Libya that made peace between Libyans impossible. This is unacceptable; it is a violation the U.N. arms embargo," he said.

"Critical to (the resolution of the) Libyan crisis is to increase international cooperation with African countries. We need international cooperation with the U.N. Security Council," he urged.

"Africa has been put aside in relation to Libya ... We believe it is absolutely essential to associate the African Union in searching (for) a solution to the Libyan conflict," he added.

"I still support African Union's decision to convene an inter-Libya reconciliation forum after Brazzaville summit," he added.

Libya has remained beset by turmoil since 2011, when long-time ruler Moammar Gadhafi was ousted and killed in a bloody NATO-backed uprising after four decades in power.

The oil-rich country has since seen the emergence of two rival seats of power: one in eastern Libya, with which putschist Gen. Khalifa Haftar is affiliated, and the Tripoli-based Government of National Accord (GNA), which enjoys U.N. recognition.

Since early April, forces loyal to Haftar have launched a campaign to capture Tripoli from the forces of the GNA.

On the situation in the Sahel region, Guterres described the U.N.-sponsored army to fight terrorism in the Sahel region as "peacekeeping where there is no peace to keep."

He said the multinational counterterrorism force deployed in the region "lacks resources and adequate financing."

The U.N. chief said he advocates a stronger African force in the region to counter terrorism.