* Metal workers could down tools from month-end

* No end in sight for platinum strike (Adds details)

By Tiisetso Motsoeneng and Mfuneko Toyana

JOHANNESBURG, June 5 (Reuters) – South Africa’s main manufacturing union said on Thursday a strike was “inevitable” and the leader of a five-month platinum walkout said his wage demands were “non-negotiable”, piling more pressure on an economy battered by labour unrest.

More than 200,000 workers led by the National Union of Metalworkers of South Africa (NUMSA) could down tools over higher pay from the beginning of July, union leaders told reporters.

“Drawing from our past experiences, a strike is inevitable,” said NUMSA General Secretary Irvin Jim. “As a worker-controlled union, we will afford our members an opportunity to determine out next course of action.”

The union is demanding a one-year 15 percent wage increase from companies that include Bell Equipment and Scaw Metals.

Separately, the president of the main platinum union rejected a government-brokered wage offer, dashing hopes for an end to a strike that has cut global platinum output by 40 percent.

“The 12,500 rand ($1,200) is still non-negotiable. AMCU members are steadfast and we are not turning back,” Joseph Mathunjwa, the president of the Association of Mineworkers and Construction Union (AMCU), told Reuters, referring to the union’s monthly wage demands.

About 70,000 AMCU members downed tools in January at Anglo American Platinum, Impala Platinum, and Lonmin in a strike that has heavily affected economic output in Africa’s most advanced economy.

The walkout in the platinum belt caused South Africa’s economy to contract in the first quarter and has raised fears it could lead the country into its second recession in five years.

STRIKE SEASON

South Africa is nearing the beginning of its annual “strike season”, in which unions negotiate with employers and sometimes strike when talks go sour.

A NUMSA walkout would weigh on key sectors such as auto parts supply and steel production, and could halt work on building projects that include power utility Eskom’s Kusile and Medupi power stations.

The rand has shed about 6.5 percent since June last year, weighed down by sluggish economic growth and high inflation.

NUMSA said it was in separate wage negotiations talks with ArcelorMittal South Africa, a unit of the world’s top steel maker, and was “very close” to sealing an agreement.

NUMSA brought auto production last year – which represents around 6 percent of economic output – to a standstill with a four-week walkout at parts manufacturers. ($1 = 10.7745 South African Rand)