Two of Nigeria's oil workers unions have renewed their threat to strike, demanding that the manager of an oil servicing firm leave the country. A strike could paralyze Port Harcourt, the hub of Nigeria's oil industry.

Leaders from the unions known as PENGASSAN and NUPENG say they will strike, unless oil services firm WASCO fires its general manager or he leaves the country by February 9. The ultimatum follows failed government mediation to break the deadlock between workers and the Malaysian owned firm.

The dispute began over workers benefits a year ago when WASCO took 50 workers off regular contracts, depriving them of benefits. It escalated recently after workers accused management of racial discrimination.

Staff at WASCO started a strike a week ago, but went back to work after the government intervened in discussions.

Union officials say WASCO has met all their demands, except for the firms continued refusal to fire the general manager, Mike Walker. WASCO officials, including Mr. Walker, have not commented publicly.

NUPENG union general secretary Bernard Ugbi says this is a sensitive issue for workers, as it is vital to create a good working environment.

"The issue I think is so sensitive because we believe in a friendly atmosphere and we believe too that whoever manages industry should understand that it is not only machines that you have to concentrate on," he said. "You have to manage human beings so they too can feel part and parcel of the establishment. But, you know, a situation whereby ego comes in, then there is a problem."

London-based oil analyst Olivia Amaewhule says this is a minor issue, but it is also a warning of future problems between management and workers, as the Nigerian government is trying to increase the number of Nigerians working for foreign companies.

"I think it is possibly a warning sign to just how quickly things can deteriorate in Nigeria," she said. "There is this local content policy that it is pushing for. It wants up to 50-percent of employees in oil companies to be Nigerian. When you increase the number of Nigerians working in these oil companies, then it makes it easier for these sorts of situations to occur."

Mrs. Amaewhule says that foreign firms will have no choice except to increase the number of their Nigerian employees, if they want to continue working in the country.

If the unions call a strike they have threatened to shut down Port Harcourt and one of four Nigerian oil refineries. Analysts say the work stoppage could reduce oil production by 500,000 barrels a day.

Nigeria is one of the world's 10-biggest oil exporters, with most of its crude going to the United States.