Ethiopia said on Monday it would temporarily host the force but the mission would only have administrative, not operational status.

The 1,700-strong U.N. mission started work in 2000, at the end of a two-year war between the two Horn of Africa neighbors that killed an estimated 70,000 people. They have been stationed in a 25-km (15.5-mile) buffer zone inside Eritrea.

The two countries insist they will not start another war, but both have moved tens of thousands of troops to the border. U.N. officials have said U.N. soldiers were reluctant to leave because they feared it could spark a new conflict.

Advance units of the force, known as UNMEE, began moving by road to designated relocation sites on the Ethiopian side of the border on Monday while the main body began moving earlier on Thursday, U.N. spokeswoman Marie Okabe said.

So far, some UNMEE convoys had been allowed to cross the border without obstruction while others had been stopped and later allowed to cross or asked to turn back, Okabe told a news briefing.

She gave no further details but said the United Nations was talking to authorities in Eritrea, which has been increasingly reluctant to host the force, to ensure instructions were issued to their troops and officials to allow the relocation.

Despite having ended their war, Ethiopia and Eritrea remain deadlocked over their 1,000 km (620-mile) border. An independent commission charged with marking the frontier awarded the town of Badme to Eritrea in 2002, but Ethiopia has refused to implement the ruling before more talks.

IMMOBILIZED

In November, the commission marked the boundary by map coordinates in a ruling Asmara accepted, but Addis Ababa rejected.

Eritrea, which has long accused the international community with siding with its much larger neighbor, cut off fuel supplies to UNMEE at the beginning of December and has ignored U.N. pleas to resume them.

"Without the fuel needed to conduct its operations, the mission has been effectively immobilized and rendered unable to carry out its critical functions," Okabe said.

She said U.N. Secretary-General Ban Ki-moon regretted that the relocation had become necessary despite a letter he sent Eritrean President Isaias Afwerki on January 21 asking him to resolve the situation.

Eritrea has said the peacekeepers' continued presence along the border was tantamount to occupation.

The U.N. Security Council renewed UNMEE's mandate for six months on January 30 despite a proposal by Ban for an extension of just one month. Diplomats said the council felt a short extension would mean submitting to "blackmail" by Eritrea.