The Navy periodically conducts sonar drills along the East Coast, the Gulf Coast, Hawai'i and the Pacific Northwest to practice hunting submarines in nearshore waters.

The California Coastal Commission earlier this year allowed the Navy to conduct the military exercises over a two-year period only if it took safeguards to protect marine mammals and sea turtles.

Among the restrictions imposed by the commission were avoiding coastal waters with a large whale and dolphin population and lowering sonar levels during periods of low visibility.

The Navy, in turn, sent a letter to the commission, saying it couldn't agree with the restrictions and will go ahead with the maritime exercises, according to the lawsuit.

"The actions of the Navy ... will lead to serious impacts on California's coastal resources," the suit said.

The commission contends it has the power to limit the Navy's training exercises to make sure it complies with a state law that protects coastal and marine resources.

The use of sonar has been linked to harmful effects on whales and other marine mammals worldwide. A congressional report last year found the Navy's sonar exercises have been blamed on at least six cases of mass death and stranding among whales in the past decade.

Sonar technology bounces pulses of sound off underwater objects to detect threats. However, environmentalists have blamed sound waves for hurting whales, possibly by damaging their hearing.

In a separate lawsuit, a coalition of environmental groups led by the Santa Monica-based Natural Resources Defense Council faulted the Navy for failing to prepare an environmental impact statement on the planned drills. It's the fifth time the NRDC has sued the Navy over the sonar issue.

The Navy had previously said many factors can cause marine animals to be beached including pollution and starvation.

On the Web:

California Coastal Commission: http://www.coastal.ca.gov