Talks between Nigeria and Cameroon over the disputed oil-rich Bakassi peninsula have ended without agreement.
Most Bakassi residents consider themselves to be Nigerian
Under a World Court ruling, Nigeria was supposed to hand the land to Cameroon last month - but it failed to do so.
Nigeria's foreign minister said the handover would definitely take place, "it is just a matter of time".
A statement after the meeting said the matter was being referred back to UN Secretary General Kofi Annan and the two countries' presidents.
"After deliberation on the issue, and as a result of a
divergence of views, the mixed-commission decided to refer the matter to the heads of state of Cameroon and Nigeria and the Secretary General of the United Nations," said a joint statement issued after the meeting in the Nigerian capital Abuja.
The matters on which the countries disagreed were not explained.
Bakassi juts into the Gulf of Guinea - which it is thought could contain up to 10% of the world's oil and gas reserves - south of the border between the two countries. It is also rich in fish.
After a long-running border dispute, the
International Court of Justice in October 2002 ordered
Nigeria to cede sovereignty of the 1,000-sq-km (400-sq-mile) territory to Cameroon.
Many border villages have changed hands, but a 15 September deadline for the final handover passed without any movement, with Nigeria citing "technical difficulties".
There has been fierce opposition to the change of sovereignty from the Bakassi people and Nigerian MPs, who say the estimated 300,000 residents of the peninsula should be allowed a referendum on their future.
The UN representative at the talks, Ahmedou Ould-Abdallah, said Nigeria must obey the court ruling.
"They cannot be the exception, the only country
not to accept international law," he said.
Minister Bola Ajibola told The Associated Press: "We want
to make sure we execute the project in the right way and at
the right time... It is just a matter of time".
And Cameroon's Justice Minister
Amadou Ali sounded optimistic, saying: "There's no doubt that they will apply