Eritrea has rejected a plea from UN Secretary General Kofi Annan to lift a ban on peacekeeping flights along its tense border with Ethiopia.
More than 3,000 UN peacekeepers patrol the border
Eritrean President Isaias Afwerki told Mr Annan: "You cannot claim the legal, political, moral or humanitarian high ground on matters of law."
Eritrea banned UN helicopter flights in its airspace on 5 October.
Eritrea and Ethiopia fought a bitter war that ended in 2000 with 70,000 dead. A border dispute still festers.
An independent commission set up under the peace deal said the border town of Badme should go to Eritrea, but Ethiopia did not accept the decision.
The two sides are now trading insults, the BBC's Elizabeth Blunt says.
Ethiopia accuses Eritrea of secretly moving troops to the border, while Eritrea says Ethiopia is not to be trusted.
Eritrea is suffering from a prolonged humanitarian catastrophe, the UN says, with 2.3 million people facing a lack of food.
More than 3,000 UN troops patrol the border zone under the terms of the December 2000 peace plan that followed a two-year border war.
Mr Annan has warned that the UN may have to pull its troops out if the flight ban remains in place.
He emphasised that both governments had the primary responsibility to bring about peace and security.
Earlier this year, the UN expressed concern over a build-up of Ethiopian and Eritrean troops close to the border zone.
Eritrea became independent from Ethiopia in 1993, after Ethiopian and Eritrean rebel movements overthrew the Derg regime in Addis Ababa.