The Supreme Court on Monday stepped into a dispute over the Navy's use of sonar off the Southern California coast and its potential harm to dolphins and whales.

Acting at the Bush administration's urging, the court agreed to review a federal appeals court ruling that limits the use of sonar in naval training exercises.

Sonar, which the Navy uses primarily to locate enemy submarines at sea, can interfere with marine mammals' ability to navigate and communicate. There is some evidence that the technology has caused whales to strand on shore.

The administration says the decision by the 9th U.S. Circuit Court of Appeals in San Francisco jeopardizes the Navy's ability to train sailors and Marines for service in wartime.

The government also says national security interests can trump those of marine mammals, and that its use of mid-frequency sonar in training exercises hasn't caused any documented harm to dolphins or beaked whales.

The Navy applauded the high court's intervention.

"The Navy's position has been the same since the first court case. This is an issue that is essential to national security and we welcome the Supreme Court's decision to hear the case," said Admiral Larry Rice, the director of the Chief of Naval Operations' Environmental Readiness Division.

Rice said the restrictions placed on the Navy in earlier court rulings, if not overturned, could cripple training exercises.

The Natural Resources Defense Council, who along with four other advocacy groups sued the Navy over the issue, contends there are ways to use sonar and to protect wildlife.

"It's clear ... that the Navy can reduce the risk of this harm by commonsense safeguards without compromising our military readiness," Joel Reynolds, director of NRDC's Marine Mammal program, said in a statement.

Although the science is inconclusive, there is strong evidence that sonar affects marine mammals. The Navy's own environmental assessment of the use of sonar in 14 training exercises off the California coast found it could disturb or harm an estimated 170,000 marine mammals, including temporary loss of hearing in at least 8,000 whales.

Some environmentalists said the Supreme Court's hearing of the case will finally settle what takes precedence — national security or environmental protection.

"This will decide whether or not the Navy is fulfilling its security goals in a way that doesn't leave massive collateral damage," said William Rossiter, president of Cetacean Society International, one of the plaintiffs in the case.

Lower courts concluded there would be near certain harm to marine life in Southern California if the Navy proceeded with sonar exercises as planned.

An injunction by a federal judge in Los Angeles early this year created a 12-nautical-mile no-sonar zone along the coast and ordered the Navy to shut off all sonar use within 2,200 yards of a marine mammal. That prompted President Bush to step in and sign a waiver exempting the Navy from a section of the Coastal Zone Management Act so training could continue as the government appealed the decision.

But the 9th Circuit sided with the lower court and said the Navy must abide by the injunction. However, while the litigation was under way the appeals court gave the Navy leeway to lessen the restrictions if it determined it was in a critical maneuver point, so that sonar shutdown would begin at 1,000 meters (about 1,093 yards) and full sonar shutdown would come at 200 meters (about 219 yards). Those are the restrictions the Navy is currently operating under.

Arguments will take place in the next court term, beginning in October.