LOS ANGELES-In a remarkable turn, conservationists and the developer of the controversial Playa Vista development here say they have reached a preliminary agreement that would preserve another 20% of the 1,087-acre project as wetlands and stop the proposed construction of more than 4,400 homes and 220,000 sf of commercial space.

The deal gives the nonprofit Trust for Public Land a one-year option to buy up to 193 acres of environmentally sensitive land next to Marina del Rey from developer Playa Vista LLC. It would be added to the 340 acres of marsh and scrubland that the builder previously agreed to restore in order to build the project.

Reed Holderman, executive director of the trust's California operations, says his group will now begin negotiating with Playa Vista on a final sales price while simultaneously trying to raise cash to close the purchase. The state has already pledged to contribute $25 million toward the deal, but the developer has estimated that the 193 acres are worth $200 million.