WASHINGTON - The U.S. Navy on Tuesday said it had asserted the "state secrets" privilege in a lawsuit by environmental groups, a move to keep the military from being forced to disclose information about the use of sonar believed to injure whales and other animals.

Navy Secretary Donald Winter, in a court filing submitted on Monday, said the information requested by plaintiffs was classified and its disclosure "could reasonably be expected to cause exceptionally grave damage to national security."

The state secrets privilege, if upheld, renders information unavailable for litigation. It can be challenged, although the federal government often succeeds in asserting the protection.

The Navy action is the latest in a string of Pentagon moves to derail a lawsuit brought by environmental groups, including the Natural Resources Defense Council, that say sonar used in routine training and testing violates environmental laws.

Those groups also argue the Navy's sonar injures and kills marine mammals, including whales and dolphins.

A spokesman for the Natural Resources Defense Council was not immediately available to comment.

In January, the Pentagon exempted the Navy for two years from a law protecting whales so that it could continue using the sonar during training. That removed one legal avenue for environmental groups to challenge Navy sonar.

The Navy said Tuesday's action should keep it from complying with requests from the plaintiffs in the lawsuit for specific information on all non-combat use of military sonar.

Plaintiffs 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 U.S. Navy anywhere in the world, according to the court filing.

A Navy official said the information requested by plaintiffs would hurt both U.S. national security and relationships with countries that participate in naval exercises with the United States.

"We were left no other alternative but to assert the state secrets privilege," the official said. "We're being asked to make public properly classified information. Our role is to provide for this nation's security and providing that information would be detrimental to that mission."