Talks aimed at ending a bitter oil dispute between Sudan and South Sudan have ended without agreement.

The six-day talks in Ethiopia's capital, Addis Ababa, finished early Wednesday. South Sudanese officials said late Tuesday that the sides remain far apart on a deal. Another round of talks is due to begin February 22.

Landlocked South Sudan took three-quarters of Sudan's oil when it gained independence in July, but must rely on the north's pipelines and export facilities.

The two countries disagree on how much South Sudan should pay for this, and Khartoum has started taking southern oil to make up for what it says are unpaid fees. South Sudan responded by shutting down all oil production.

The south's chief negotiator, Pagan Amum, says production will not resume unless the Khartoum government pays market value for the seized oil.

“We cannot export our oil if it is not secure and safe. If the government of Sudan is practicing state piracy, this would be very dangerous for us to do, to even send one barrel.”

Amum also said that Khartoum had recently seized a further 2.4 million barrels of oil.

Disputes over borders and accusations of cross-border attacks have raised tension between the two Sudans, and leaders on both sides have suggested the countries could go to war.

Last week, the two sides signed an African Union-brokered non-aggression pact. But on Tuesday, South Sudan accused Sudan of breaking the pact by carrying out airstrikes on a disputed border town, a charge Sudan denies.

Despite the failure of the peace talks, Sudanese negotiator Sabir Mohamed Hassan said the mood is more cooperative than past attempts.

“Both countries are feeling the heat….they both now believe that they need to sit down and talk and agree.”

The dispute is having a devastating impact on both economies. More than 90 percent of South Sudan's revenues comes from oil exports. Sudan is said to have lost more than $7 billion when the south gained independence and took over most of the oil fields.