Nigerian oil workers said they had started a strike on Tuesday that may affect exports, although market sources doubted they would have an impact since similar strikes in recent years have not significantly hurt production or exports.

Spokesman for the blue-collar oil workers’ union PENGASSAN, Babatunde Oke, said both blue- and white- collar workers were on strike over a disagreement with the government over pensions and problems with refineries.

“It will not have any impact on production but it can have an impact on exports,” he told Reuters. “All export terminals manned by our workers could shut down.”

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There was no immediate comment from the government. On Monday, government had tried to dialogue with officials of the two unions, PENGASSAN and NUPENG as they threatened to begin the strike same day. Apparently, the strike declaration showed that the talks have collapsed.

Nigerian oil workers often strike or threaten to, and there has not in recent history been any major impact on exports or production.

An official at one oil multinational said shutting down exports would be a drastic action and he doubted the union could do it.

Oke insisted that “it could affect the supply of crude by Nigeria to the world markets.”

“Until we have a commitment from the government” on demands such as fixing crude supplies to refineries and the pension gap, “the strike stays on,” he said.