HONOLULU -- Officials with the Superferry and the state said operations will go ahead despite a court ruling that could shut it down.

There were dueling news conferences and legal maneuvers on Friday by both sides.

The Hawaii Superferry announced on Friday that it plans to start with $5 fares on Sunday, two days earlier than it had planned.

"We're ready to go. Hawaii Superferry will begin commencing regularly scheduled service this Sunday, Aug. 26," said John Garibaldi of Hawaii Superferry.

The move comes a day after the Supreme Court said the state and Superferry broke environmental laws by fixing up Kahului Harbor on Maui without an environmental assessment.

Superferry opponents said they plan to block the business.

"I think the Superferry should just stop right now until they do a study and until the implement mitigation procedures. It’s a totally irresponsible way to do business in Hawaii," attorney Isaac Hall said on Thursday.

The motion to stop the Superferry will be filed Monday, opponents said.

By starting service on Sunday, Superferry officials said they hope to show widespread support for the service.

The state will ask that he balance the harm of shutting down a $300 million business verses potential harm to the environment.

"There is no environmental harm determined as yet, just all speculation and assumptions on the part of some opponents," state Department of Transportation Director Barry Fukunaga said.

State officials said they need to hear more from the Supreme Court about exactly what environmental threat the justices see before they make decisions about future Superferry projects or requests of other companies to open new businesses in Hawaii waters.