The US Navy on Tuesday played its "state secrets" joker in ongoing attempts to resist a whale-saving lawsuit by an environmental group.

The group bringing the lawsuit, the Natural Resources Defence Council (NRDC), believes high-powered naval sonar can distress, injure, or kill whales and dolphins. It is also suggested that active sonar pulses can disorient cetaceans and cause them to become stranded or lost.

Secretary for the Navy Donald Winter said in a court filing that the plaintiffs' requests for disclosure, if complied with, "could reasonably be expected to cause exceptionally grave damage to national security".

According to the Navy, the conservationists had requested information on the latitude, longitude, time and date, duration, and name of the exercise for every non-combat use of military sonar by the US Navy anywhere in the world.

The NRDC describes itself as "the US nation's most effective environmental action organisation", and it doesn't intend to let the navy get away with the state secrets ploy.