Negotiations over the 36-month contract have been lengthy and at times fractious, with members voting to reject a previous offer and strike on March 9.
A 200,000-strong Brazilian claimant group failed to resurrect a 5.0 billion pound ($6.9 billion) English lawsuit against the mining giant over the Fundão dam failure.
For the first 12 months of the year, the market was in a 559,000 tonnes deficit compared with a 383,000 tonnes deficit in the same period a year earlier.