Matson Inc. and three of its unions averted a potentially crippling shipping strike for the islands Friday after agreeing to new, tentative, four-year contracts.

A strike would have affected Matson shipping operations in Hawaii, Seattle, Los Angeles and Oakland, Calif.

“We have a signed agreement with the unions,” said Matson spokesman Keoni Wagner. “It is subject to ratification, but we’re pleased to have reached a fair and equitable agreement, and service will continue uninterrupted.”

Three of Matson’s unions — the Sailors’ Union of the Pacific; the Seafarers International Union — Atlantic, Gulf, Lakes and Inland Waters; and the Pacific Coast Marine Firemen, Oilers, Watertenders and Wipers Association — reached tentative agreements on new contracts with Matson on Friday following negotiations at the Sailors’ Union headquarters in San Francisco.

Company and union officials declined to provide details of the agreements because union members still need to vote on whether to ratify them at different times and locations this month in Hawaii and the West Coast cities.

Gunnar Lundeberg, president of the Sailors’ Union of the Pacific, said, “There is no strike. We reached an agreement. Matson did the right thing. Our fair and reasonable proposals were ultimately accepted, and we reached an agreement. It will be business as usual.”

The current contracts were scheduled to expire at 9 p.m. Hawaii time Friday, or midnight on the West Coast.

Instead, Matson and the three unions reached agreements at 5:42 p.m. California time Friday, said Anthony Poplawski, president of the Pacific Coast Marine Firemen, Oilers, Watertenders and Wipers Association.

“We bargained in good faith, both sides, and came to an agreement about six hours before we had to,” Poplawski said. “We don’t anticipate any problems with ratifying the contract.”

Poplawski acknowledged the inconvenience that a shipping strike would have had on island consumers and said, “Nobody wins in a strike, but sometimes you’ve got to do it.”

Going into Friday’s negotiations, Lundeberg said Matson and the unions had been “poles apart” on issues including wages, hours, working conditions and benefits.

For an island state that relies on imports, Matson ships bring in about two-thirds of all goods imported into Hawaii. Eight Matson ships arrive from West Coast ports every two weeks.

Matson, which has provided Hawaii service since 1882, also delivers goods to and from Alaska, Guam, Micronesia and the South Pacific from its mainland ports.

If union leaders had called for a strike, other Matson unionized workers likely also would have gone on strike and honored picket lines in Hawaii and along the West Coast.

The result would have left goods stranded on Hawaii and West Coast docks — and aboard shuttered ships.

Matson has 1,925 employees, and 712 are covered by union contracts.