U.N. Secretary General Kofi Annan is urging Eritrea to lift a ban on United Nations helicopter flights along its border with Ethiopia.


U.N. helicopters in Eritrea were grounded Wednesday after the government ordered them to stop flying missions in support of peacekeeping operations.


Sokesman Stephane Dujarric confirmed that the order is being strictly observed.


"We would not be flying helicopters in contradiction of a government order not to fly them. We need their permission to fly them," he said.


The helicopters are mainly used to re-supply U.N. peacekeepers in the region, as well as for aerial reconnaissance and medical evacuation missions. Spokesman Dujarric said halting the flights could heighten mutual suspicions along the Ethiopia-Eritrea border and create instability.


Earlier, Secretary-General Annan said the Eritrean government had given no reason for grounding the helicopters. He urged officials in Asmara to change their minds.


'I hope the Eritrean government will reverse its decision to ground all the U.N. helicopters, placing the U.N. peacekeepers at risk.  The government has a responsibility to support and ensure the protection of these peacekeepers and I hope that the message has got through," he said.


A spokesman for the U.N. peacekeeping office confirmed Wednesday that helicopters were continuing to fly on the Ethiopian side of the border. He noted that helicopters are the main source of supplies for the 3,000 U.N. peacekeepers in the region.


The Security Council held an urgent meeting at Secretary-General Annan's request Tuesday to discuss rising tensions in the Horn of Africa. Afterward, the Council issued a statement urging Eritrea to reverse the helicopter flight ban, and calling on both countries not to resume their border war.


Ethiopia and Eritrea signed a peace deal in 2000 ending more than two years of fighting. They agreed to have an independent commission settle the border dispute. But the demarcation process broke down in 2002 after Ethiopia objected to the commission's decision to grant Eritrea sovereignty over a disputed town.


A senior Eritrean official warned last month that fighting could resume unless the United Nations intervenes to settle the dispute.