The UN's Libya mission insisted on Tuesday that planned peace talks in Geneva would go ahead the following day, after rival sides separately said they would not take part.
The announcement came after a parliament based in eastern Libya, backed by military commander Khalifa Haftar, said it would not take part because the United Nations Support Mission in Libya (UNSMIL) had not approved all of its representatives.
A rival authority in Tripoli, the High State Council - the equivalent of a senate - also said it would not participate in the talks set for Wednesday until progress was made in military negotiations.
But UNSMIL spokesman Jean Alam told AFP that the "Libyan Political Dialogue will start tomorrow as planned".
The talks are set to bring together 13 delegates each from the parliament and the High State Council, along with other figures invited by UN envoy Ghassan Salame.
Haftar's forces launched an offensive against Tripoli, seat of the UN-recognised Government of National Accord (GNA), last April.
His fighters have since stalled on the edges of the capital, but fighting has left over 1,000 people dead according to the UN.
A joint military commission with five members from each side wound up talks Sunday in the Swiss city with a "draft ceasefire agreement" to be finalised in March, according to the UN mission.
Libya has been rocked by violence since a NATO-backed uprising in 2011 overthrew and killed veteran dictator Moamer Kadhafi.
Since 2015, the UN-recognised Government of National Accord, based in Tripoli, has been vying with Haftar's forces for control.