Juba- Sudan's former civil war foes failed to agree on how to conduct a referendum on independence for the south on Thursday, with one side blaming a lack of trust.

North and south Sudan fought a two-decade war that ended with a peace deal in 2005, but tensions remain and time is running out to prepare for two deadlines in the accord -- a national election scheduled for 2010 and the referendum in 2011.

Leaders from both sides meeting in the south's capital Juba said they had failed to reach an agreement on how the referendum should be organised and had not even got round to discussing a contested census, a building block for elections.

The failure will raise fears for the roll-out of the 2005 Comprehensive Peace Agreement in the oil-producing nation, where analysts have said wrangling over politics and disagreements over the sharing of oil revenues could reignite conflict.

Armies from the two sides have clashed since 2005 and the south has said it will not accept any delay to the referendum.

The lead negotiator for north Sudan's dominant National Congress Party Ghazi Salaheddin said the sides had only managed to agree on one issue -- a definition of who was eligible to vote in the referendum.