The United Nations on Monday accused Eritrea of moving 1,500 troops and 14 tanks into a buffer zone established after a 2 1/2-year border war with Ethiopia in "a major breach" of a cease-fire agreement reached in 2000.

CountryWatch: Eritrea

Eritrean troops also took over a U.N. checkpoint and forced a platoon of Jordanian peacekeepers to leave, U.N. officials said.

Secretary-General Kofi Annan urged the Eritrean government to withdraw its troops from the buffer zone immediately, and to cooperate with the United Nations in restoring the cease-fire arrangements, U.N. spokesman Stephane Dujarric said.

Relations between Eritrea and Ethiopia have been consistently strained since Eritrea gained its independence from the Addis Ababa government in 1993 following a 30-year guerrilla war. Eritrea's action raised the threat of renewed war between the feuding Horn of Africa neighbors.

CountryWatch: Ethiopia

A 3,800-member U.N. peacekeeping force has been monitoring a buffer zone 15 miles wide and 620 miles long between Eritrea and Ethiopia under the December 2000 agreement reached in the Algerian capital, Algiers, that ended the border war.

In apparent frustration at Ethiopia's refusal to implement a binding ruling on their disputed border, and the lack of U.N. action to pressure Ethiopia to comply, Eritrea banned U.N. helicopter flights in its airspace in October 2005. Two months later, it banned U.N. night patrols and expelled Western peacekeepers.

The international boundary commission's ruling in 2002 awarded the town of Badme to Eritrea, but Ethiopia has refused to accept the decision — even though under the Algiers accord both countries agreed it would be binding.

U.N. peacekeeping officials said the buffer zone is divided into a western sector manned by a Jordanian battalion and a central sector manned by an Indian battalion.

There was no immediate information on how far into the buffer zone the Eritrean troops and tanks had moved, the officials said on condition of anonymity because they were not authorized to speak publicly. There was also no information on whether Eritrea had massed additional troops and military hardware on the border.

Dujarric said Annan is deeply concerned about the incursion into the zone.

"This development constitutes a major breach of the cease-fire and the integrity of the Temporary Security Zone," he said. "It could seriously jeopardize the peace process and undermine the Algiers Agreements between Ethiopia and Eritrea, with potential consequences for the wider region."

CountryWatch: Eritrea

CountryWatch: Ethiopia