Russia and China on Friday opposed a US-led request to impose sanctions on two Libyans accused of obstructing UN talks on forming a national unity government, diplomats said.
Britain, France, Spain and the United States had sought the measures to shore up efforts by UN envoy Bernardino Leon to clinch a political deal before the start of Ramadan on June 17.
The four countries asked that a global travel ban and an assets freeze be imposed on Abdul Rahman Swehli, a politician from Misrata, and Othman Maliqta, commander of the Zintani Qaqa brigade.
A new crucial round of talks is opening in Rabat on Monday.
The UN sanctions committee had given the 15 members of the Security Council until 1900 GMT to raise objections.
Russia spoke out against the move, arguing that the request "had not been prepared properly but in a rush" and that it lacked evidence or documents on the two Libyans' actions, according to the response seen by AFP.
China said the political talks were "at a critical junction" and that the council "should be very careful and take more time to consider this issue".
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The sanctions request by the four countries was further complicated when Libya's UN Ambassador Ibrahim Dabbashi sent a letter to the council, casting doubt over whether the measures would be helpful.
The two Libyans are not considered high-profile, but the decision to target them first was aimed at sending a message to more senior-ranking officials that they must get onboard.
Libyan factions agreed during Geneva talks in January to set up a national unity government to restore stability that has been shattered since the 2011 fall of Moamer Kadhafi.
But months of UN-brokered negotiations have yet to produce a political accord.
Abdul Rahman Swehli is chairman of the Libyan Union for the Homeland Party who reportedly pressed for an attack by Libya Dawn militias against the oil port of Sidra in February to disrupt the talks and strengthen his position.
Othman Maliqta commanded forces that attacked the parliament in Tripoli in May 2014, using trucks mounted with anti-aircraft guns, mortars and rocket fire.
Libya has two sets of rival parliaments and governments, with Tripoli controlled by Libyan Dawn forces who seized the capital last year, forcing the internationally recognized government to operate out of Tobruk, in the east of the country.
The chaos has turned the north African country into a staging ground for migrant smuggling across the Mediterranean to Europe, and there is mounting alarm over gains made by extremists like the Islamic State group.