Workers at BHP Billiton Ltd.'s (BHP) Samancor manganese alloys operation in South Africa could strike this week after wage negotiations deadlocked, their union said Tuesday.

The operation has scaled back in recent months in the face of weak demand and BHP Billiton spokeswoman Bronwyn Wilkinson said the company didn't believe a strike would affect current or planned production.

"After three months of negotiations between the company and Numsa (the National Union of Metalworkers of South Africa), no agreement has been reached," Wilkinson said.

She said the company has offered workers a 7% wage increase against the union's demands for 8.8%.

Companies across industries in South Africa have been hit with demands for above-inflation pay increases and the threat of strikes. Production at Impala Platinum Holdings Ltd.'s (IMP.JO) largest mining operation in the country was halted Tuesday after underground workers put down their tools in what a spokesman for the National Union of Mineworkers said was a protest against delays in securing a wage deal.

Numsa said its members planned to strike Thursday at Samancor's operation in Meyerton, and if its demands weren't met it would call on its members at other BHP Billiton plants to join the strike in solidarity. A union spokesman said there were more than 600 members in Meyerton.

"Our members have no luxury of time to beg the filthy rich BHP Billiton management whilst on a daily basis, workers are ultra hungry and super exploited," Numsa said.

BHP Billiton's Wilkinson said the Metalloys operation was forced to suspend production for the three months earlier this year in response to poor market conditions, and it is currently running at below 50% of its full capacity.

"The company has chosen to carefully control costs rather than implementing reduced work weeks and retrenchments, in the effort to mitigate the effects of the market downturn on employees," she said.

Separately, Johannesburg-based Implats, the world's second-largest producer of the metal after Anglo Platinum Ltd. (AMS.JO), said output had been halted by a strike at its Rustenburg operation. Its Marula and refining operations continue to run as normal, it said.

The action comes as NUM consults with members over an improved offer from the company that would see pay raised 10% across the board. The union over the weekend called off a strike planned for Monday.

NUM spokesman Lesiba Seshoka said there was no clear indication yet whether most union members had accepted the offer from Implats. The company and the union are due to meet again Wednesday.

Consumer price inflation peaked at 13.7% in August last year, but has been steadily easing since then. At the same time, Africa's biggest economy is struggling with its first recession in 17 years as manufacturing and mining companies have been hit with a slump in demand.

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