State-owned mining company Solid Energy has called meetings with staff from Stockton mine.
The company announced last July it planned to lay off 184 staff from the mine, and in March its chief executive, Dan Clifford, told a parliamentary select committee further job losses were inevitable.
At the time, Mr Clifford said the stubbornly low price of coking coal, down 40 percent from its peak of a few years ago, meant job losses were a certainty.
Solid Energy said Stockton management had called an all-staff meeting in Westport tomorrow, and that would be followed by an announcement at about 4pm.
West Coast Labour MP Damien O'Connor said any job cuts at the mine, or its total closure, would have consequences throughout the South Island .
"I would hate to think that we would just shut it down. There are huge implications for Tranz Rail, the Midland Line and, indeed, the Port of Lyttelton if the operation is shut down," he said.
"So it goes way beyond that of just the direct miners themselves.
"The Government has to look at this, as the major shareholder in Solid Energy."
