Tripoli - UN envoy Martin Kobler deplored a decision by Libyan authorities to postpone the formation of a new unity government that was expected on Sunday, saying timelines must be respected.
A presidential council headed by businessman Fayez al-Sarraj had been expected to announce by Sunday a cabinet line-up as part of a UN-brokered deal to end years of bloodshed in Libya.
But the council said on its Facebook page that the formation of the much-delayed unity government "has been postponed by 48 hours", without elaborating.
Kobler, who arrived Sunday for talks with Libyan politicians, bemoaned the move.
"I regret the decision of Presidency Council to postpone the formation of the Government of National Accord. #Libya can no longer wait," he wrote on Twitter.
He called for "timelines to be respected", stressing that the Libyan people were "suffering the consequences".
"I urge Presidency Council to adhere to new timeline it has committed itself to, ensure the expeditious formation of Gov. of National Accord," he tweeted.
Peter Millet, the British ambassador to the North African country agreed, stressing that the national interests of Libyans must come first.
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"Disappointing delay. Forming #Libya Govt of National Accord is urgent to deal with #terrorism & rescue the economy," Millet tweeted.
Libya has been in chaos since the 2011 ouster of longtime dictator Moamer Kadhafi and now has two governments and parliaments.
On December 17, under UN guidance, envoys from both sides and a number of independent political figures signed a deal to unify the government.
Around 80 of 188 lawmakers from Libya's internationally recognised parliament, based in the east of the country, and 50 of 136 members of the rival Tripoli-based General National Congress signed the deal.
It calls for a 17-member government, headed by Sarraj, and based in the capital.
The United Nations is pressing all sides to the Libyan conflict to accept the power-sharing deal, amid concerns the Islamic State jihadist group is gaining influence in the country.
On Sunday, Kobler held private talks with the speaker of the internationally recognised legislature, Aguila Saleh, to discuss the latest developments, the national news agency LANA reported