Workers in northwest Ohio have joined the first nationwide strike at US oil refineries since 1980.
The Blade newspaper of Toledo reported that some 100 BP-Husky Toledo refinery workers began picketing at midnight on Sunday outside the plant in Oregon, Ohio.
A local union official said on Saturday night that about 350 workers would be on strike and planned to start picketing around the clock.
The strike began after negotiations with Shell Oil Company, which is also negotiating the national contract for other oil companies, broke down.
The Ohio workers are joining about 3,800 steelworkers who began a strike on February 1 at refineries from California to Kentucky.
"They're discouraged that the strike is happening, but they understand why it has to happen," said Bryan Sidel, financial secretary of the local union.
The United Steelworkers union earlier notified BP Plc that workers at refineries in Ohio and Indiana would join the walkout.
The union has said workers want better health care benefits and limits on the use of contractors to replace union members in maintenance jobs.
A spokesman for the United Steelworkers told Al Jazeera the strike was not about wages.
"The main thing that we want people to understand is that this is not a financial strike, it's about safety and going home to our wives and our children," he said.
A BP spokesman said the company expects to continue operating with replacement workers and does not expect a significant effect on production.
"BP is disappointed that USW leadership decided to call a strike at both the Whiting Refinery and BP-Husky Toledo Refinery," said BP spokesman Scott Dean in an email to the AP news agency.
He said BP remained at the negotiating table and wanted a deal that "provides good wages while giving management the flexibility it needs" to remain competitive.
BP's plant in Whiting, Indiana, has about 1,860 employees, more than 1,000 represented by the steelworkers. BP's Toledo refinery in Ohio, which it owns 50-50 with Canada's Husky Energy, has some 600 workers total.
The plants will be staffed by replacements including retirees and former front-line workers who now hold salaried jobs, Dean said.
Source: Al Jazeera And AP