NEWPORT, R.I. (AP) — The group that owns The Breakers mansion is declaring victory in its long-running battle to build a visitors center on the grounds of the national historic landmark, following a decision by the Rhode Island Supreme Court.

Visitors center opponents said Tuesday they're disappointed they have lost in the court, but said they're launching a campaign to pressure the Preservation Society of Newport County to abandon the plan and "to preserve the historic integrity of The Breakers."

The high court on Saturday declined to intervene in an attempt to block zoning approval for the project. The Preservation Society says it will now move forward. The nonprofit group's board chairman, Monty Burnham, called it "exceptionally good news for the more than 450,000 people who visit The Breakers each year from around the world."

"Having modern hospitality for visitors to this National Historic Landmark is vital. It's time now to set aside the differences over this project and move on to strengthen Newport's future," Burnham said in a statement.

The society's lawyer told The Newport Daily News the group will now work to hire a contractor and get needed permits. He said a groundbreaking could happen within months.

The Preservation Society, which owns several Gilded Age mansions in the resort town, says the building is needed to provide more modern restroom and ticketing facilities, as well as a place for visitors to buy sandwiches and snacks.

Opponents, including members of the Vanderbilt family that built The Breakers, a neighborhood group and some local and national preservationists say a visitors center will ruin the historic character of the landscape. They say the issue could be solved by putting the new building in the parking lot across the street.

Some opponents have started a new group, called Friends of Newport Preservation, which plans to launch its campaign on Thursday. The group on Tuesday also released a letter, written by Benjamin Lenhardt, chairman of the New York-based Garden Conservancy.

Lenhardt's letter expresses "strong concern" about the plan, and says it "would destroy all or part of crucial design elements" in The Breakers landscape.

The Preservation Society did not immediately respond to a request for comment about the letter or plans for a public campaign.