Nicaraguan Foreign Ministry official Cesar Vega said Costa Rica violated a court ruling when officials from the Convention on Wetlands of International Importance, or Ramsar, inspected a disputed border area in March, the Tico Times reported.
"We are going to notify the court that Costa Rica is not complying with the provisional order because the same ruling allows us to do so," Vega said.
The dispute emerged in 1998 when Nicaragua forbade the transit of Costa Rican policemen in the San Juan River and imposed a fee and visa requirement for any Costa Rican tourists who used the river.
The court ruling said both countries must keep military and other official delegations out of the area unless accompanied by members of Ramsar and prior notice is given.
Nicaraguan officials say they weren't notified prior to the visit and have yet to receive an official Ramsar report describing the inspection.
Costa Rican officials responded by accusing Nicaragua of acting in "bad faith" by trying to prevent Ramsar specialists from inspecting the area.