WEST PALM BEACH, Fla. -- A massive Everglades restoration project will be put on hold pending the outcome of a lawsuit by environmentalists, a move that could end up costing the state nearly $14 million just for the delays.

The board of the South Florida Water Management District voted Thursday to halt construction of a mammoth reservoir, bigger than Manhattan, designed to revive the ecosystem of the once-famed River of Grass.

The 25-square-mile aboveground reservoir - the largest of its kind in the world - is estimated to cost up to $800 million and was set for completion in 2010. The district has already spent about $250 million on construction.

No one disagrees that storing runoff water is key to reviving the Everglades, but the restoration effort has for years pitted environmentalists against the government.

The Natural Resources Defense Council sued over the reservoir, claiming the state has not legally committed itself to using the water primarily for restoration efforts.

The state insists at least 80 percent of the water will be for environmental purposes, but critics fear that without a legally binding agreement, the water could be sent elsewhere for agriculture or development.

Council attorney Brad Sewell said the intent of the lawsuit is not to stop construction, but to bind the district legally to its own resolution passed last year by its board agreeing the water will be used mostly for the environment.

The district, however, fears that if a federal judge revokes its permits for the project because of the lawsuit, millions of dollars could be lost.

"It will be much more expensive if we got into the middle of this contract and then all of a sudden it gets shut down," said district spokesman Randy Smith. "The board's decision was made solely on prudent financial responsibility to the taxpayers."

The district board anticipates construction could be halted through the end of the year. The board agreed to stop construction as of June 1 and begin paying its contractors $1.9 million for each month the project is delayed, up to $14 million by the end of 2008. The district also is not ruling out the possibility that the project could be terminated altogether.

"It makes no sense for them to stop this reservoir because of our litigation," Sewell said. "We have never tried to stop this reservoir. Everyone agrees that the Everglades desperately needs more storage to provide more water flows."

Water once flowed practically unhindered from the Everglades headwaters south of Orlando all the way into Florida Bay. But now when a hard rain falls, canals direct the overflow into the ocean to keep from inundating 5 million people who have settled in the area. It also has left the wetlands parched and near ecological collapse.

That's where the massive reservoir just south of Lake Okeechobee comes in. Its intent is to store up to 62 billion gallons of water that would normally be channeled out to sea and instead divert it into the Everglades at various times to mimic a more natural flow.

The entire wetlands once covered more than 6,250 square miles, but have shrunk by half, replaced with homes and farms and a 2,000-mile grid of drainage canals. In the process, the Everglades has lost 90 percent of its wading birds, and 68 threatened or endangered species face extreme peril.

The overall Everglades project, including the reservoir, is the largest such wetlands restoration effort in the world. Much of its cost was supposed to be split 50-50 by the federal government and the state. But because Congress hasn't allocated its share, many aspects of the work have been delayed.

In 2000, the key parts of the restoration were estimated to cost $7.8 billion and take 30 years to finish. The price tag has now ballooned by billions of dollars because of rising construction and real estate costs.