PORTLAND — A dispute over whether the planned sale of Maine's largest daily newspaper must include a contract that represents hundreds of union employees has landed in federal court.

MaineToday Media, Inc., the Seattle Times Co. subsidiary that owns the Portland Press Herald/Maine Sunday Telegram, filed a lawsuit Tuesday in U.S. District Court in Portland against the Portland Newspaper Guild.

The lawsuit comes three months after the Seattle Times Co. announced that it was putting its daily newspapers in Portland, Augusta and Waterville up for sale. Since then, the newspapers have announced layoffs and an employee voluntary severance offer, citing increases in energy and newsprint costs and a drop in advertising revenue.

The lawsuit asks a federal judge either to declare that the 2007 contract between the newspaper and the union does not require the newspaper to include the contract as part of any sale, or to order the union to go to arbitration to settle the dispute.

Publisher Chuck Cochrane said in an interview today that uncertainty over whether a potential buyer would have to assume the guild contract has stalled sales talks.

The union contract, which expires in 2011, states that the agreement "shall inure to the benefit of and be binding upon the successors and assigns of the Publisher."

In an e-mail to newspaper employees, Cochrane said of the lawsuit, "The company reluctantly took this step only after repeated attempts failed to convince the guild's leadership to voluntarily agree to resolve this matter through an expedited arbitration."

Before filing the lawsuit, the company met twice with guild leaders to discuss the dispute, but did not get the sense that the guild wanted to resolve the issue in a timely manner, Cochrane said.

"Even though the owners of MaineToday Media, Inc. do not believe that a buyer can be forced to assume the guild contract," Cochrane's e-mail continued, "they are willing to ask prospective buyers if they will agree to do so voluntarily. However, none of the interested parties has so far indicated any inclination to accept the current contract as it is written."

Representatives of the newspaper guild could not immediately be reached for comment Wednesday.

The full lawsuit filing can be read here.