Washington  - The US Supreme Court said Monday it will hear the Navy's appeal of a ruling that restricts the use of sonar off the California coast to protect marine life.

A federal judge on February 4 ruled against the Navy, rejecting President George W Bush's waiver that granted the service an exemption from environmental regulations limiting the use of sonar during training missions.

The federal court in Los Angeles ruled the Navy must follow rules that restrict the use of the powerful radar designed to find and track submarines, and enforce a buffer zone within 20 kilometres of the California shore.

The active sonar must also be shut down if marine mammals are spotted within 2,000 metres of the ships, under the current rules.

The Navy and environmental groups have been sparring for years over the health effects of the sonar on sea life. The Navy says it already takes steps to minimize the impact on whales, dolphins and other mammals and that the training is vital to national security.

Environmentalists argue the effects of sonar can harms the creatures and can cause whales to beach themselves. The Natural Resources Defence Council brought the legal challenge on behalf of a handful of other environmental groups.

"It's clear both that high intensity military sonar can injure and kill whales, dolphins, and other marine life and that the Navy can reduce the risk of this harm by commonsense safeguards without compromising our military readiness," Joel Reynolds, director of the marine protection at the NRDC said Monday.

The NRDC is ready to argue before the Supreme Court, Reynolds said. The high court will hear the case this fall.

The Navy welcomed the decision, while noting that it has instituted 29 measures to protect sea life, including lookout stations, passive acoustic monitoring for marine mammals and setting up safety zones to reduce the sonar power or shut it down if marine life is spotted.

The Navy said it strives to find a balance between the need for an effective combat force and protecting the environment, and that the measures backed by NRDC harm force readiness.

"These restrictions make it very difficult to conduct the kind of realistic, integrated training exercises that ensure the combat effectiveness of our force," said Vice Admiral Samuel J Locklear, commander of the US Third Fleet in San Diego, California.(dpa)