U.N. monitors say the disputed border between Ethiopia and Eritrea remains tense and potentially volatile, with continued troop movements on both sides of the frontier.

U.N. officials in the region say they continue to be hampered in their border monitoring mission by Eritrean restrictions on helicopter flights and patrols.

The chief of the staff of the regional U.N. mission, Colonel Mohammed Iqbal of Bangladesh, says Ethiopia has redeployed two to three divisions to within 15 kilometers of the border, officially on training maneuvers.

He says an undetermined number of Eritrean militias have moved into a buffer zone on the border, saying they are harvesting crops.

Colonel Iqbal says the U.N. is only monitoring 40 or 45 percent of the border's central and western zones because Eritrea has banned U.N. helicopter flights, and ground patrols are frequently stopped at checkpoints.

A U.N. spokeswoman in Asmara, Gail Bindley-Taylor-Sainte, says there is concern either side might make a blunder that could spark war.

"Because of our degraded ability to monitor, it opens the door for miscalculation and any miscalculation could lead to something that none of us want to think about," said

Gail Bindley-Taylor-Sainte.

The U.N. comments come a day after Ethiopian Prime Minister Meles Zenawi played down the likelihood of war, saying he would not respond to any provocations short of a full-scale invasion by Eritrea.

The two countries fought a war between 1998 and 2000, which killed an estimated 70,000 people. Eritrea wants Ethiopia to implement a border map drawn up in 2002 by an independent commission. Ethiopia says the map unfairly divides some villages and family farms.

U.S. Undersecretary of State Nicolas Burns discussed the situation last week with Prime Minister Meles and underlined the U.S. intention to work with the United Nations to de-escalate the situation.

A U.N. peacekeeping envoy, Japanese Ambassador Kenzo Oshima, visited Ethiopia and Eritrea this week and called on both governments to prevent the current situation from deteriorating.