Association of mineworkers and construction union (AMCU) president Joseph Mathunjwa. Picture: Tiro Ramatlhatse.

Rustenburg - Shop stewards from South Africa's striking Amcu mining union urged leader Joseph Mathunjwa to sign a wage deal with the three major platinum firms on Thursday at a dramatic mass rally crowning nearly five months of industrial action.

Cheers erupted from the crowd of thousands of miners as one senior union official took the microphone to declare: “Sign, Mathunjwa, sign.”

“This union has worked. We want this money. We come from hardships. Amcu has worked. We can't take kids to school. Sign Mathunjwa,” another union leader added.

Earlier, the three platinum firms - Anglo American Platinum , Impala Platinum and Lonmin - said they had reached “in principle undertakings” with the leaders of the longest strike in the history of South Africa's mines.

They did not disclose details of the offer.

“The principles that underpin the proposals seek to achieve a sustainable future for the three platinum companies for the benefit of all stakeholders and to afford employees the best possible increase under the current financial circumstances,” Lonmin said in a statement.

Shares in Lonmin jumped almost 8 percent, while Impala Platinum stock climbed 1.5 percent.

However, Anglo American Platinum slipped around 1 percent.

Spot platinum prices fell more than 2 percent.

The strike by the 70,000 Amcu members which started in January dragged Africa's most advanced economy into contraction in the first quarter of the year, and piled pressure on the rand because of the threat to foreign exchange earnings. - Reuters