The USW also accuses Beijing of direct violations of China's agreement with the WTO.

A renegotiation with the USW could add costs for Apollo.

The USW represents workers at 64 percent of U.S. refineries.

Those losses, a USW lawyer claims, indicate the subsidy was a violation of trade rules.

The USW represents workers at plants accounting for 64 percent of U.S. refining capacity, Baker said.

William Steers, a spokesman for ArcelorMittal USA in Chicago, did not comment on the USW action.

The USW's previous contracts with U.S. Steel and ArcelorMittal had both expired at midnight on Saturday.

Instead the union found delays and frustration in committees stacked against them, said a USW vice president.

The USW was invited to add more members, said David Miller, API director of standards, but did not.

Gary Howe, president of USW Local 1005 in Hamilton, criticized U.S. Steel Canada for rejecting the latest offer.

If it is ratified by the members, it must also be approved by USW International officials in Pittsburgh .

Only its rough surface and the earplugs gave clues to what it might be: a USW, an ultrasonic weapon.

We remain optimistic about reaching a fair and equitable contract with the USW, he said in an e-mail to Reuters.

In a week of face-to-face negotiations in Austin, Texas, the USW has rejected three contract offers from Shell, Baker said.

The USW has said cutting the workforce while the refinery continues full production could reduce safety due to worker fatigue.

USW confirmed it had rented space in London, but having "tested the market" had decided not to proceed.