Ceasefire monitors in Sri Lanka are pressing the Tamil Tigers to grant access to an airstrip that the rebels possess in the north of the country.
The head of the Monitoring Mission, Hagrup Haukland, said the refusal to grant access to the strip amounted to a violation of the ceasefire.
The mission wants to verify government claims the rebels have two aircraft.
The Sri Lankan government says the airstrip violates the country's ceasefire agreement.
But the rebels insist that the airstrip existed before they entered the truce.