The United Nations envoy to Libya, Slovakian Jan Kubis, resigned from his post on Tuesday, a month before the scheduled presidential elections in Libya, diplomatic sources at the United Nations said.
It is not yet clear why Kubis, 69, is stepping down.
The sources, who refused to reveal themselves, suggested that the resignation was due to Jan Kubis' insistence that he not move to Tripoli to work from the Libyan capital, and that he was satisfied with assuming his duties from several European capitals.
The sources added that the United Nations is unofficially proposing the appointment of the veteran British diplomat, Nicholas Kay, as his successor.
The appointment of the new envoy must be approved by the UN Security Council.
Kubis is a former foreign minister of Slovakia, and served as the United Nations special coordinator for Lebanon and the UN's special envoy to Afghanistan and Iraq.
The Security Council had approved his appointment as a special envoy to Libya in January of this year, to succeed Ghassan Salame, who resigned from the post in March of last year due to stress.
His sudden withdrawal from the Libyan file comes the day after the closing of the nomination process for the presidential elections scheduled for December 24.
The High National Elections Commission in Libya said that the final number of candidates for the presidential elections was 98, including two women.
A UN political forum last year called parliamentary and presidential elections for December 24 as part of a road map to end the civil war, but disagreements over the planned elections threaten to frustrate the UN-backed peace process.
A first round of presidential elections is scheduled for 24 December, while parliamentary elections have been postponed to January or February, but the rules for the elections have not yet been agreed upon.