BHP Billiton Ltd. (BHP) plans to lay off 150 of the 950 employees at its Hotazel Manganese Mines in South Africa due to a drop in demand for the ingredient in steel production, a trade union said Monday.

Solidarity in an e-mailed statement said the process of cutting jobs has been launched with the independent Commission for Conciliation, Mediation and Arbitration, or CCMA.

"There are several alternatives that should be considered first and therefore the retrenchment of the 150 employees should be considered as a last resort," union spokesman Jaco Kleynhans said, adding Solidarity hoped the consultation process with CCMA would be used to limit the number of job cuts.

Hotazel operates the Wessels and Mamatwan mines outside Hotazel in the Northern Cape province.

"The pressure on the communities of the Northern Cape is now reaching alarming levels," Kleynhans said. "The region's mines, including diamond and manganese, in particular are being affected by the economic climate."

-By Robb M. Stewart, Dow Jones Newswires; +27 11 783 7848; robb.stewart@dowjones.com