For months it seemed that Williamsburg’s new waterfront park was a sure thing. But this week, the park’s future may be shattered by the bang of the auction gavel.

The 15-acre stretch of private property abutting the East River is due to be auctioned off on Tuesday by a Dutch bank that owns the long-neglected parcel. According to an official with the state Department of Environmental Conservation (DEC), the bank doesn’t think it can fetch a high enough price from the state, so it will seek highest-bidder private sector buyers.

By law, the state cannot bid at the auction–which makes it unlikely the land will ever be purchased for a park.

“There has to be more open space in under-served urban areas,” said Cathy Peake, chief of staff to Assemblyman Joseph Lentol, who represents parts of Williamsburg.

Things looked a lot brighter earlier this year. The would-be park was the lone open-space site in any low-income New York City neighborhood slated for purchase through the state environmental Bond Act. Later, it became the only such property that the state legislature placed on the annual Environmental Protection Fund list.

But those Cinderella days came to an end this spring when Governor Pataki vetoed the more than 30 sites on the Fund list, saying that the legislature had weighed the bill down with pork.

The governor later made an unsuccessful bid to restore every single open space parcel–except the Williamsburg property. “There’s no reason to have left this site off the list,” said John Stouffer, legislative director for the Atlantic Sierra Club chapter. “It’s more of a priority list, not all of the land on the list will be acquired in any given year.”

But the fight may not be over just yet. DEC officials say they will try to negotiate with the land’s new owners–even though they can’t, by law, pay more than market rate for the site.

Neighborhood activists say they will pressure the state to reclaim their lost land. “This is the line in the sand on open space,” says Samara Swanton, executive director of Williamsburg’s Watchperson Project “Not because the site is in a pristine area. It’s on an OK site in a low-income area. If we lose this fight, we can lose the fight for parks in urban areas.”