Because of restrictions imposed by the Eritrean government, U.N. personnel are down to their last remaining emergency reserves of diesel fuel to power generators, vehicles and other equipment for the 7 1/2-year-old peacekeeping operation.

At last count, that operation had about 1,500 troops and 200 military observers, along with several hundred civilians and dozens of volunteers based out of Asmara, Eritrea and Addis Ababa, Ethiopia.

"We're basically going to have to move our troops out at some point, because we're not getting any more fuel," a U.N. diplomat said. "We would relocate to Ethiopia. It would not be the end of the mission, we would just not be present in Eritrea."

Eritrea gained independence from Ethiopia in 1993 after a 30-year guerrilla war, but the border between the two was never formally drawn up. Tens of thousands were killed in a border war that erupted in 1998.

Most of the U.N. personnel have been used to patrol territory on the Eritrean side.

"They are making plans to evacuate because they are down to their emergency reserves of fuel, and if they don't get the fuel and they have no way of getting the fuel in, that would endangers the lives of troops there," said a senior official within Secretary General Ban Ki-moon's office.

All the officials and diplomats spoke to the AP on condition of anonymity, because they said Ban hadn't yet announced his final decision.

Officials at Eritrea's mission to the U.N. could not be reached for immediate comment on Friday.

Under a 2000 peace deal, both sides agreed to accept an international boundary commission's ruling on the border dispute — and the U.N. formally began trying to keep the peace in July 2000.

The commission proposed a border in 2002, but Ethiopia has refused to accept it because the proposal awarded the key town of Badme to Eritrea.

Now, Eritrea appears to be trying to use the diesel supplies to force the U.N. to resolve its dispute with Ethiopia.

The secretary-general said in a recent report to the council that with generators used at camps and some field checkpoints for only two hours a day, peacekeeping patrols have been cut back and field staff have struggled to stay in touch.

Ban had set Wednesday as a deadline for making a decision, since he said there were only a few days of diesel supplies left and the reserves were intended for emergency evacuations.

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