Almost 300 coalminers at BHP Billiton’s West Cliff mine will walk off the job next week in a move that is likely to grind production to a halt, the workers’ union says.Construction Forestry Mining and Energy Union (CFMEU) members at West Cliff will begin a seven-day strike next Wednesday unless a deal is reached in an ongoing pay dispute.Mining and energy district vice-president Bob Timbs said the workers would take protected action in response to the company’s latest offer, which failed to meet employee demands.‘‘The company is sort of going backwards with their offers so the only place for us to go forwards is to start taking this industrial action,’’ he said yesterday.BHP Billiton subsidiary Illawarra Coal operates the West Cliff mine, one of several to supply the Port Kembla Coal Terminal (PKCT), where strike action is also brewing.Illawarra Coal head of external affairs John Brannon yesterday confirmed an employee ballot was conducted at West Cliff and the ballot supported taking protected action.‘‘The company has not been notified of any protected action at this stage and discussions with the union are continuing,’’ he said.Mr Timbs said the company had been notified yesterday afternoon.The CFMEU is pushing for 4.5 per cent pay rises and changes to the existing bonus scheme.‘‘We’re asking for something that we believe is comparable to other BHP Billiton operations,’’ Mr Timbs said.‘‘I hope that we don’t have to carry through with the industrial action as we are meeting with the company on Tuesday and hope to come to some agreement.’’A potential strike at the coal terminal, also due to start next Wednesday, was unrelated, he added.Union officials met PKCT management yesterday but it is understood little progress was made. General manager Peter Green said a conciliation conference with Fair Work Australia will be held tomorrow.