At least 4,500 workers in three states walked off the job this week in the first major labor action against the timber industry this year in the Pacific Northwest.

The strike began at midnight Sunday at 18 mills in Oregon, Washington and Montana, said Bill Hubbell, president of the International Woodworkers of America-U.S.The strike by the IWA and the Western Council of Industrial Workers affected 1,300 workers at 10 Willamette Industries Inc. mills in Linn and Benton counties in Oregon; 2,400 at six Champion International Corp. plants in Oregon, Washington and Montana; and 800 at two Eastern Oregon mills of DAW Forest Products Co.

The decision to strike was the "only decision left for us to come up with," said Hubbell.

"We are at a complete negotiating impasse with these companies, and they refuse to even consider our initial industry settlement," added Mike Draper, executive officer with the Western Council.

Draper referred to a tentative long-term agreement that his union and the IWA reached last week with Bohemia Lumber Co. in Eugene, affecting more than 800 workers. The agreement was the first settlement in the 1988 bargaining year, and the two unions plan to use it as a foundation for future negotiations.

Bill Latimer, Willamette Industries division manager, declined to comment on the unions' strike plans Sunday, saying only, "We'll just wait and see what happens."

Attempts to reach officials at Champion headquarters in Cincinnati and DAW in Oregon were unsuccessful late Sunday.

Pickets first began appearing Sunday evening at Champion International mills in Missoula and Bonner, Mont., where 900 union members are employed.

On the picket line Sunday evening, mill workers at Bonner said they were seeking a fair wage after years without any substantial increase.

"I'm making the same hourly rate I was 10 years ago," said Bonner employee Rick Zenke. "Do you think you could live on that?"