(Corrects throughout with 90-day open season ending on July 31, not starting July 1)

By Yereth Rosen

ANCHORAGE, Alaska, Nov 3 (Reuters) - As long as energy companies participate in 2010's open season for a massive, yet-to-be-built Alaska gas pipeline, TransCanada Corp (TRP.TO: Quote, Profile, Research) will be on track in its plan to construct the project and start delivering to U.S. markets by 2018, Alaska officials said Tuesday.

Even if energy producers' gas-shipping offers are contingent on fiscal concessions that do not exist, the open season will have been a success as long as TransCanada wins enough interest and confidence to continue work on the 1,700-mile Prudhoe Bay-to-Alberta mega-project, the officials said.

An open season that leads immediately into financing and project sanction is not a "litmus test" for TransCanada's success, said Alaska Revenue Commissioner Pat Galvin.

"They're looking for a level of commitment necessary to say, Is this project worth investigating further?'" Galvin said at a news conference.

For the state, any shipping offers, no matter what conditions are attached, "will produce us with a window into the types of things that need to be addressed to make this project successful," he said.

TransCanada, which earlier this year joined in a partnership with Exxon Mobil Corp (XOM.N: Quote, Profile, Research), one of the three major North Slope oil producers, is the state's preferred pipeline sponsor and holder of a state license issued last year under the Alaska Gasline Inducement Act, or AGIA.

The act, pushed by former Gov. Sarah Palin, authorizes the state to provide up to $500 million in funding to TransCanada and forbids the state from entering into gas pipeline negotiations with any competing sponsors.