The Mercury understands managing director Rex Wright will meet workers at 8.30am today to deliver the news.

Yesterday there was speculation among workers concerned whether Coalcliff or Corrimal Cokeworks would close.

A company spokeswoman said Mr Wright was unable to comment and any news of a closure was "pure speculation".

The coke maker, which celebrated the 100th anniversary of Corrimal Cokeworks this year, employs about 50 workers across both plants.

United Mine Workers district secretary Graham White said he had heard on Monday of plans to close one of the plants by the middle of next year.

He said the union and workers were expecting the news.

"We have been expecting [Illawarra Coke Company] to be one of the places to come offline for a while," he said.

Mr White said the number of job losses and redundancies would depend on which site was marked for closure, but believed the company was being "fair" in giving workers six months to adjust to the change.

"We'll work our way through whatever announcement [Mr Wright] makes and try to limit the impact as best we can," he said.

"We've got to wait and see what the numbers are going to be."

In his company's December newsletter, Mr Wright noted that 2012 had been "extremely challenging". He said market conditions for [the company] have been difficult since the global financial crisis but last year the high price of coal and the low price of coke, combined with the strong Australian dollar, made it worse.

The introduction of the carbon tax added to this already heavy burden, and in August the Mercury reported that the company learnt its annual carbon liability would be double what was expected, at more than $500,000 per year.