An unexpected spike in project costs for the Edgartown Public Library expansion project left library trustees scrambling for a solution this week, as a plan to ask town voters for $4 million was scrapped when it was discovered that the actual need would be significantly higher.

At a Wednesday meeting of the Edgartown financial advisory committee, library trustees said that they would need closer to $5.4 million from the town by this coming June to secure a $4.6 million grant from the Massachusetts board of library commissioners.

And now the project is in a state of confusion as the town weighs the pros and cons of waiting for another round of state grant funding to come through next year. Library trustees, finance committee members and selectmen all agreed that the project may need to go back to the drawing board, despite all the best efforts to raise public and private money to pay for it.

“Time is money,” said library trustee and board chairman Patricia Rose at the meeting. “If we go with a different design, we may lose some of the private funding.”

There is also the chance that the next round of state grants will not come through, and even if it does, the town will end up losing money it already has spent on the project. For example, the $3.5 million voter-backed purchase of the Captain Warren House, located next to the library building on North Water street, would no longer be considered as part of the town’s contribution to the project in future grant applications, as it is with the impending June grant.

As a result, the amount of money the town would have to put into the project would probably be significantly more, said Ms. Rose.

But finance committee members and the town selectmen still said it would be best to wait. Selectman Arthur Smadbeck said the next grant round would give the project a better chance of getting more support from the town. “This is an opportunity for you to reach out to the town and say — let’s make this a town project,” Mr. Smadbeck said.

Finance committee member Morton Fearey Jr. agreed; he said hasty action could only serve to hurt the project. “If you go with this, it’s a very divided project,” he told the trustees.

The project began five years ago with the purchase of the Warren House, and has run into a series of setbacks since then. The original plan called for converting the Warren House to a library annex, and then renovating the Carnegie library, a historic building. But it was later determined that the Warren House would have to be torn down. Building design and parking requirements were the subject of much back and forth discussion before the town zoning board of appeals finally approved the project. Even then, after spending the initial $3.5 million for the Warren House, library trustees expected the remaining funds for the project to come from private donors. A foundation was formed to help raise the money. But donations fell short, and to date only about $1 million has been raised from private funds.

The total cost of the project is nearly $15 million. Facing a June 15 deadline to come up with matching money for the state library grant, trustees were forced to turn back to the town. And now what was originally expected to be a $4 million gap has turned out to be closer to $5.4 million, due to cost adjustments which were determined this week.

Mr. Fearey told library trustees bluntly that their fund-raising prospects appear bleak. “In fund-raising, you need three or four big gifts, and you don’t have that. That’s going to make fund-raising exceptionally difficult until you get it,” he said.

Mr. Smadbeck concurred. “The money isn’t out there in the private sector to build Edgartown a new library,” he said, adding: “I’m talking about abandoning the idea of doing it privately. I think the best selling point to anyone that’s willing to support our library is that this is a town project that everyone is behind.”

Ms. Rose conceded that fund-raising has been an uphill battle. “We’re disappointed because we wanted to do better than that,” she said. But she said there could be a silver lining; a new project design could attract new donors and might also open the door for incorporating greener building practices. “We’re interested in ideas about how to proceed,” she said finally.

Another meeting has been set for next week to discuss a warrant article that would help the library renovation project start over again.

Meanwhile, library trustees said they were concerned about what would become of the money they’ve already raised for the project.

The finance committee agreed that the town should draft a letter to donors explaining the situation.

And while all parties agreed to put the project on hold in anticipation of another round of state grant funding, questions remain about the future prospects of landing the grant. “You’re going to have a hard job selling this,” finance committee vice chairman Laurence Mercier told the trustees.

If the next round of grant money comes through, applications would be due by January of 2011. The start date for construction would be December of 2012.