European Union envoys met in Juba on Thursday with Lord's Resistance Army rebel representatives in a bid to unblock peace talks to end a brutal two-decade insurgency in northern Uganda, officials said.

The envoys, who travelled from Kampala to the talks' venue in the southern Sudanese capital of Juba, "told the rebels the urgency of resuming talks," a southern Sudanese mediator told AFP.

The talks stalled late November after rebels walked out, claiming the army had attacked a rebel unit and killed three fighters who were headed to one of two neutral camps in southern Sudan.

"The EU ambassadors called for serious participation of both parties in the talks," LRA spokesman Obonyo Olweny told AFP.

"They pressed for a conclusive end of the talks and told us that the international community and the people of Uganda were waiting for a peace agreement," he said.

The envoys also met the Ugandan government delegation to the talks, but it was not immediately clear what they discussed.

On Wednesday, Kampala said it was ready to resume talks to end the conflict that has killed tens of thousands and displaced nearly two million others.

"We have spent three weeks in consultations and confidence-building," said Interior Minister Ruhakana Rugunda, who leads the government negotiating team.

"This period allowed us to strengthen the peace process," he said.

Officials said both sides were due to meet the southern Sudan mediators later Thursday to renew a truce that expired on December 1 to avoid fresh flare-ups in fighting as talks remained stalled.

"We hope to extend and improve on the truce this evening," Olweny said.

But the LRA said it would not resume "substantive" talks with the government until the Uganda People's Defence Forces (UPDF) withdraw from positions in southern Sudan.

"Substantive talks will resume only when the army pulls out and paves the way for our forces to gather at the assembly points," Olweny said.

Under the terms of the landmark August truce that was renewed in November, LRA fighters are to gather at two neutral camps for the duration of the negotiations.

But their arrival has been repeatedly delayed by allegations of government truce violations.

The Juba talks are seen as the best chance to end the deadly conflict which has been described as one of the the world's worst humanitarian crisis, marked by LRA brutality against civilians and accusations that the army has done the same.

The LRA took over leadership of a two-year-old regional rebellion in 1988 to overthrow President Yoweri Museveni.