July 16 (Bloomberg) -- Unionized technicians at Petroleo Brasileiro SA, Brazil's state-controlled oil company, will conduct a 48-hour work stoppage in support of striking offshore oil workers in the Campos Basin.

The sympathy strike will begin tonight at midnight, according to a posting late yesterday on the Petroleum Workers' Union's Web site. The Campos workers are pressing for an extra day of pay for each two weeks worked offshore and a greater share of the company's profits.

Operations aren't likely to be halted at refineries and other facilities targeted by the strike, Helio Seidel, the union's national coordinator, said in an interview today. Rather, it will serve as a warning of more serious actions if the Campos Basin strike isn't resolved, he said, without estimating how many workers will take part.

Union members at Petrobras, as the company is known, will refuse to report to work at the shift change tonight, forcing those who remain on duty to reduce their work load to maintain essential services, Seidel said.

``We decided to unite to show the company that this problem has to be resolved,'' he said. ``If not, we'll have a nationwide strike, including other unions, starting Aug. 5.''

Petrobras preferred shares, its most-traded class of stock, fell 78 centavos, or 1.9 percent, to 39.77 reais in Sao Paulo.

Unified Demands

The sympathy strike aims to unify the contract demands of Oil Worker Federation chapters. The one representing 4,500 workers at the Campos Basin offshore oil platforms began a five- day strike July 14 seeking an extra day's pay for their 14-day- on, 21-day-off shifts on offshore oil platforms. Other chapters are seeking larger payments under the company's profit-sharing and bonus plans.

Petrobras set up a contingency plan in Campos, the source of about 80 percent of Brazil's oil, and platforms were producing at full capacity as of yesterday, according to the company. It also put in place a contingency plan at the refineries and other units targeted in the latest strike, according to statement today read by a press officer.

``We respect the union's right to strike and are open to negotiation,'' the company said. ``We are still waiting for a response to our previous offer.''

The union plans to vote on a proposal related to the demands for larger profit-sharing and bonus plans by July 24, Seidel said.

To contact the reporters on this story: To contact the reporters on this story: Jeb Blount in Rio de Janeiro at jblount@bloomberg.net; Laura Price in Sao Paulo at lprice3@bloomberg.net.

Last Updated: July 16, 2008 16:29 EDT