PORTLAND – A year after it introduced a discounted season pass for Sunday River in Maine and Attitash in New Hampshire, American Skiing Co. announced Monday it is offering a money-saving pass that can be used at all six of its Eastern resorts.

The “All For One Pass” is the latest wrinkle in a price war that began a year ago when American Skiing slashed the cost of a full-price adult pass at Sunday River and Attitash by up to 75 percent to compete with New Hampshire’s “Threedom Pass.”

The Threedom Pass, which was introduced about five years ago, offers discount rates on season tickets that can be used at Waterville Valley, Loon and Cranmore.

The latest announcement by American Skiing expands its two-resort pass to include Killington, Mount Snow/Haystack and Pico in Vermont and Sugarloaf in Maine.

Skiers and snowboarders can purchase the six-resort pass for $349 with 14 blackout days during holidays and school vacations. Another one of the five options allows unlimited skiing every day of the season for $599. Those prices are valid until Aug. 30.

The Threedom Pass is even cheaper. The unlimited version goes for $459 and the pass with blackout days is $319. In addition, there is a $269 option that excludes Saturdays.

Prior to the introduction of the discount pass, the cost of a season ticket at any of the six American Skiing resorts in the Northeast was $1,049, said Susan DuPlessis, spokeswoman for Sunday River.

She said last year’s experiment at Sunday River and Attitash was successful, prompting the company to expand the program.

“We sold about four times the number of season passes that we traditionally sold for Sunday River alone,” DuPlessis said.

She said the company expects buyers of the six-resort passes to remain “somewhat loyal to their home resort” while having the option to try some of the others. Some skiers may “follow the snow” by traveling to the area that offers the best skiing, she added.

American Skiing said it plans to limit the number of All for One Passes to avoid overcrowding.

“We are very aware of the balance needed in the number sold and when they can be used so as to keep the high level of experience that our guests are accustomed to,” said Chip Carey, the company’s senior vice president for sales and marketing.

Kathy Bartlett, marketing director for Waterville Valley, Cranmore and Loon, dismissed concerns that American Skiing’s new combined pass would draw business from her company’s resorts.

Maintaining that the Threedom Pass offers the best value, she said its sales were unaffected by last year’s introduction of the Sunday River-Attitash pass.

“People ski particular ski mountains for very personal reasons, and a lot of it is determined by geography,” she said. “What we find is that you’re taking your skiers who would typically buy day tickets and converting them into season ticket buyers.”

The concept of multiple-resort season passes was first tried in Colorado before expanding west to California and east to New England.