The Navy said Saturday the deal reached with the Natural Resources Defense Council and other groups requires it to continue to research how sonar affects whales and other marine mammals.

It doesn't require sailors to adopt additional measures to protect the animals when they use sonar.

The agreement comes one month after the U.S. Supreme Court ruled in favor of the Navy in another sonar lawsuit the NRDC filed.

"The Navy is pleased that after more than three years of extensive litigation, this matter has been brought to an end on favorable terms," Frank R. Jimenez, the Navy's general counsel, said in a statement.

NRDC officials could not immediately be reached for comment. The plaintiffs asked the judge to dismiss the case on Friday.

The NRDC and five other plaintiffs filed the lawsuit in federal court in the Central District of California on October 19, 2005.

The complaint sought a court order to curb mid-frequency sonar, the Navy's preferred method for detecting enemy submarines, on the grounds the sonar disturbs and sometimes kills whales and dolphins.

The Bush administration, in arguments Wednesday, is asking the court to undo lower court rulings that limited the use of sonar in naval training exercises off the coast of Southern California.

Sonar, which the Navy relies on to locate enemy submarines, can interfere with whales' ability to navigate and communicate. There is also evidence that the technology has caused whales to strand themselves on shore.

The exercises have continued since the 9th U.S. Circuit Court of Appeals in San Francisco ruled in February that the Navy must limit sonar use when ships get close to marine mammals.

The administration says the president has the power to override federal court rulings on environmental laws during emergencies that include harm to national security. The Navy says it has already taken steps to protect beaked whales, dolphins and other creatures and is balancing war training and environmental protections.

The Natural Resources Defense Council, one of five advocacy groups that sued to force the Navy to take steps to protect the whales, argues that the Navy has to comply with environmental laws.

In a 2-1 decision, the U.S. Court of Appeals for the District of Columbia Circuit threw out a two-year-old rule that may have allowed some refineries, power plants and factories to exceed pollution limits because the Environmental Protection Agency "failed to fix inadequate monitoring requirements ... and prohibited states and local authorities from doing so."

Since 1990, the Clean Air Act has required permits granted to facilities releasing more than 100 tons of any pollutant a year to include enough monitoring to ensure the company is meeting its emissions targets. Approximately 15,000 to 16,000 permits have been issued under the program, mostly by state and local pollution agencies.

"We can't have strong enforcement of our clean air laws unless we know what polluters are putting into the air," said Keri Powell, a staff attorney with Earthjustice, who sued the EPA on behalf of four environmental groups.

The EPA said Tuesday that it was reviewing the court's decision. But an agency spokesman said the monitoring deficiencies should be remedied on the national level rather than on a case-by-case basis.

Appeals court judge Brett Kavanaugh, a former attorney in the Bush White House, wrote the sole dissenting opinion.

He said that while EPA and state and local governments may disagree about whether monitoring requirements will adequately measure compliance, he found "nothing in the statute that prohibits EPA's approach."

In a brief order, the court said the 9th U.S. Circuit Court of Appeals, based in San Francisco, should decide the matter of interest arising from punitive damages for victims in the 1989 Exxon Valdez disaster.

Stanford University law professor Jeffrey Fisher, an attorney who represents commercial fishermen, Native Alaskans, landowners, businesses and local governments in the case, said justices rejected Exxon Mobil's bold attempt to take away interest.

"It's nice to see the court refusing to do the outlandish thing Exxon wanted," Fisher said.

The issue is whether interest accrued since 1994, when a federal jury first awarded punitive damages for the supertanker's spill of 11 million gallons of crude oil into Alaska's Prince William Sound.

The company contends that if interest is paid, it should be calculated from the date the punitive damages were awarded by the Supreme Court, not all the way back to 1994, said Exxon Mobil spokesman Alan Jeffers. The company will pursue that contention with the 9th Circuit.

The 9th U.S. Circuit Court of Appeals said it agreed with the federal judge who in 2005 ruled that the EPA exceeded its authority in exempting certain ship discharges from the pollution control requirements of the 1972 Clean Water Act.

A handful of environmental groups and states sued the EPA to require it to regulate ballast water because of concerns that invasive aquatic species such as mollusks were being pumped into local waters.

Except for sewage, ship discharges are exempt from regulation. Wednesday's court ruling applies to bilge water and non-sewage wastewater from a ships' showers, laundries, galleys and engines.

While the EPA was appealing the judge's decision, it also drafted regulations requiring oceangoing freighters to dump ballast water at least 200 miles from shore and refill their tanks with new seawater to flush and kill invasive freshwater species.

The agency is taking public comments on the regulations, which would take effect Sept. 30.

"We're reviewing the decision to determine next steps," Benjamin H. Grumbles, EPA's assistant administrator for water said in a statement. "It's commonsense and good environmental policy not to require millions of boaters and vessel owners to get federal clean water permits."

The ruling comes as efforts to establish a federal standard for cleaning up ballast water have stalled in Congress. Among other issues, California officials have expressed concerns to lawmakers that the state's stricter standards could be pre-empted by a weaker federal law.

Some environmental groups contend the EPA's plan to block foreign species does little to prevent exotics from slipping into U.S. ports and water bodies.

"It's a good first step," said Nina Bell, executive director of Northwest Environmental Advocates, one of the groups that brought the lawsuit. "But the EPA's got a long way to go when it comes to regulating ballast water."

Numerous invasive species have devastated aquatic ecosystems throughout the country. In the Great Lakes, global hitchhikers such as the quagga mussel and the freshwater ruffe fish out-compete native species for food, spread disease and cost the regional economy billions a year.

Six states, including New York, Wisconsin and Pennsylvania, joined as plaintiffs in the suit. A shipping industry group joined the EPA in fighting the regulations.

From July 2006 through December 2007 there were 304 instances where the EPA found what would have been violations of the Clean Water Act before the court's ruling, according to a memo by the agency's enforcement chief.

Officials "chose not to pursue formal enforcement based on the uncertainty about EPA's jurisdiction," according to the memo, which was released Monday by two Democratic House committee chairmen.

The EPA also chose to "lower the priority" of 147 other cases because it was unclear whether the intermittent streams, swamps and marshes flowed into navigable waterways.

The U.S. Court of Appeals for the District of Columbia denied a petition by 17 states and several environmental groups asking it to order the Environmental Protection Agency to make that determination within 60 days.

Such a finding is a necessary first step to regulating carbon dioxide and other greenhouse gases from motor vehicle tailpipes and the smokestacks of refineries, power plants and factories. The Supreme Court more than a year ago ruled that the EPA has the authority to regulate greenhouse gases under the Clean Air Act, a step President Bush has repeatedly refused to take.

Instead, EPA is expected to issue a proposal in coming weeks that seeks public comment on a range of options the agency could take to control greenhouse gases under current law.