SAN DIEGO -- A decision by the Navy to reject rules by the California Coastal Commission to protect whales and other marine mammals from sonar training exercises raised the possibility Tuesday of a legal clash with the commission or a leading environmental organization.

The coastal commission is beginning a three-day meeting today in San Diego that will include consideration of its next move in the dispute, which intensified Monday when the Navy notified the commission it would not comply with the rules. Mark Delaplaine, a staff member, said the commissioners will conduct part of the meeting in closed session to consider the possibility of a lawsuit against the Navy. Meanwhile, the Navy is forging ahead with sonar training, perhaps as early as today.

Joel Reynolds, a lawyer with the Natural Resources Defense Council, said his organization was prepared to sue the Navy if the coastal commission did not.

The Navy's rejection of the rules came in a letter to Peter Douglas, executive director of the coastal commission, from Rear Adm. C.J. Mossey.

The letter says any harm done to whales and other sea creatures is not significant enough to adopt the rules. Navy officials said in a statement released Monday that they could not conduct effective training under the new rules.

The Navy says sonar training is essential to defending commercial shipping lanes against a looming threat by a new generation of ultra-quiet diesel submarines. Environmentalists have cited scientists' investigation of whale strandings in Greece, the Bahamas, the Canary Islands and other parts of the world as irrefutable evidence of the threat sonar training poses to marine mammals.

Mossey's letter to Douglas argues that any effects on whales' behavior caused by sonar training are "temporary" and harmful only to a few individual whales.

The letter also contends that the coastal commission has no legal authority over sonar training exercises, which are usually conducted 75 miles or more out at sea. The coastal commission's rule-making power encompasses a three-mile zone off the coast. It has also invoked its authority over activities outside the three-mile limit that are deemed likely to harm the environment within the three-mile limit.

Jon Yoshishige, a spokesman for the Pacific Fleet in Hawaii, said the Navy would be conducting sonar training exercises in waters off Camp Pendleton either today or Feb. 23.

- Contact staff writer Joe Beck at (760) 740-3516 or jbeck@nctimes.com.