ANCHORAGE, Alaska (Reuters) - A federal mediator on Monday suspended contract talks aimed at settling a strike that has shut down Alaska’s state ferry system at the peak of the tourist season, with services to more than 30 coastal communities halted for a sixth straight day.

The strike comes amid deep budget cuts for the state-owned ferry network, known as the Alaska Marine Highway System, with services to several communities scheduled to cease entirely at the end of the summer and not resume until the summer of 2020.

No new bargaining sessions were announced between the administration of Governor Mike Dunleavy and the Inlandboatmen’s Union (IBU) of the Pacific, which represents more than 400 deckhands and other state ferry employees who walked off the job last Wednesday.

It marked the first strike in 42 years against the state-owned ferry network.

Most of Alaska’s ferry-served communities, including Juneau, the capital, can be reached only by boat or plane and depend on the vessels for passenger travel and deliveries of groceries, seafood catches, vehicles and other items. The network also provided services to the ports of Bellingham, Washington, and Rupert, British Columbia.

Union leaders said they called the strike after contract negotiations that have dragged on for three years reached deadlock. Talks resumed on Saturday under the guidance of a federal mediator, with both sides largely adhering to a news blackout.

Late on Monday, however, the Dunleavy administration said the mediator “has recessed talks until a later date” following more than 20 hours at the bargaining table, and that ferry operations “remain suspended.”

There was no precise reason given for the break in negotiations, but Department of Administration Commissioner Kelly Tshibaka accused the union of seeking “wage offers that are not legally permissible.”

“The strike is unlawful because it is based on demands that are illegal under Alaska law,” she said in a statement.

Robb Arnold, vice chairman of the IBU’s Alaska regional board, said it was not a breakdown in talks, but “It’s a break.”

“The mediator’s smart,” Arnold said. “She knows what’s at stake and she’s trying to keep us going.”

Arnold said he did not want to comment on state officials’ assertions that the strike is illegal.

He said there has been progress toward an agreement, but that he could not provide details.

The IBU’s last three-year contract with the state expired in mid-2017. The union, whose rank-and-file have worked since then under short-term extensions, has accused the Dunleavy administration of bad-faith in negotiations and labor violations.

The state said the strike has cost the ferry network more than $200,000 in revenue a day. Dunleavy, a Republican in his first year as governor, has said he wants to privatize the system.

On Monday, U.S. Senator Bernie Sanders of Vermont joined two other Democratic presidential candidates in voicing support for the strike. Former Vice President Joe Biden and Senator Kamala Harris of California previously used Twitter to back the union.