BUFFALO, N.Y. — The Buffalo Sabres, parent club of the Portland Pirates, have signed a nonbinding letter of intent to purchase the Rochester Americans of the American Hockey League.

“We are two, three days into our due diligence,” a person familiar with negotiations said Tuesday. The person spoke on the condition of anonymity because of a confidentiality agreement that’s in place.

Brian Petrovek, the Pirates’ CEO/managing owner, declined to comment about the possible purchase by Buffalo, his team’s NHL affiliate for the past three seasons, and what it would mean to the future of the Pirates.

“We have a contractural relationship with the Buffalo Sabres,” Petrovek said. “They know it. We know it. I really can’t say more about it.”

Last spring, before the Sabres were sold to Terry Pagula, the Pirates and Sabres agreed to an extension of their affiliation agreement.

“The first three years (of the agreement) are iron-clad,” Petrovek said. “There is no out clause.”

The affiliation is through the end of the 2013-14 season. Buffalo has the option of ending its affiliation with the Pirates in the fourth and fifth years of the arrangement.

Petrovek declined to comment on what penalty the Sabres would face if they broke their contractural arrangement and moved their top minor league team elsewhere.

According to The Associated Press, a formal sale of the Rochester franchise to the Sabres remains months away.

A Buffalo spokesman, Michael Gilbert, said the team had no comment.

Buffalo’s interest in the Americans comes three months after Pegula purchased the Sabres for $189 million.

A Pennsylvania billionaire, Pegula, 60, is a longtime Sabres fan.

Last September, Pagula donated $88 million to Penn State, his alma mater, to fund a new multipurpose arena and help upgrade the men’s hockey program at the school.

He has an estimated worth of $3 billion and was most recently ranked 110th on Forbes magazine’s list of wealthiest Americans.

The purchase of the Americans would reunite the Sabres with their former minor league affiliate. The teams broke ties following the 2007-08 season.

The Americans’ president, Lewis Staats, had no comment, according to the team spokesman, Craig Rybczynski.

In an interview published in Tuesday’s edition of The Rochester Democrat and Chronicle, Staats said the team had been approached by more than one NHL team this year.

The Amerks’ three-year deal with the Florida Panthers expired after this season.

A sale would have to be approved by the AHL board of governors.

– Staff Writer Paul Betit contributed to this story.