By Jon Herskovitz

JOHANNESBURG, Aug 27 (Reuters) - South Africa's largest
union threatened on Friday to bring gold and platinum mining and
other industries to a halt next week in a strike to support a
labour stoppage by 1.3 million state workers.

The strike by state workers seeking pay raises more than
double the inflation rate started last week and has led to
school closures, prevented medical treatment and caused bodies
to pile up at state-run morgues.

The National Union of Mineworkers said its members would
launch the solidarity strike next Thursday, limited to one day
for now but it could be prolonged, which would deal a blow to
the mining sector in Africa's largest economy -- responsible for
5 to 6 percent of South Africa's gross domestic product.

NUM is the biggest union in the country's largest labour
federation COSATU, which says it has 2 million members and on
Thursday filed seven-day strike notices that would allow members
in affiliated unions to strike..

"The NUM fully supports the public sector strike and would
next week Thursday ensure that every mining operation, every
construction site and every energy worker joins the public
sector strike in different forms," it said in a statement.

South Africa is the world's fourth largest gold producer
and largest platinum producer, with mines turning out about 488
kg (1,076 lb) of gold and 385 kg of platinum a day.

The country's biggest firms, such as Anglo Platinum, Impala
Platinum and Harmony Gold Mining, have stockpiles of the
precious metal and would not be hard-hit if it was a one-day
work stoppage.

The NUM said on Friday some workers at a Rio Tinto-BHP
Billiton titanium joint venture had also downed tools in a
dispute over wages.

Thousands of municipal workers defied a court order and
staged a one-day sympathy strike on Friday that slowed garbage
collection in major cities.

Public Service and Administration Minister Richard Baloyi
repeated a call for essential workers including security guards,
nurses, daycare providers and sewerage maintenance workers, to
obey a court order compelling them to go back to work.

Thousands have defied the order and risk losing their jobs
if the government decides to seek punishment.

A spokesman for the minister said there were no formal plans
for negotiations but the lines of communication had been open.

"There are concerned engagements as part of the effort to
end this strike," Dumisani Nkwamba told Reuters.

BUDGET STRAIN

The government has said it cannot afford the state workers'
demand of an 8.6 percent wage rise, more than double the
inflation rate, and 1,000 rand ($137) a month as a housing
allowance. It has offered 7 percent and 700 rand.

Any agreement to end the dispute is likely to swell state
spending by about 1 to 2 percent, forcing the government to find
new funds just as it tries to bring down a deficit totalling 6.7
percent of gross domestic product.

Spending on personnel is the biggest category of state
expenditure, taking up about a third of the budget. In 2006/07,
about 35 percent of tax revenue went to paying state employees
and that rose to about 46 percent in 2009/10, which means any
wage deal could lead to increased taxes.

Jasson Urbach, an economist with the Free Market Foundation,
estimated the work stoppage was costing the economy about $150
million a day.

An expanded strike would add to worries about prospects for
growth after the economy slowed more than expected in the second
quarter of 2010 as mining contracted and manufacturing expanded
at a slower pace.

Pressure is mounting on the government to reach a deal
before it deals a significant blow to Africa's largest economy,
which might also help it mend ties with COSATU, which has said
their decades-long alliance was in jeopardy of rupture.

The unions are under the gun to reach a deal with public
opinion turning against them after strikers harassed students
trying to go to school and blocked the sick from seeking medical
care, which health officials said led to several deaths.
(Additional reporting by Peroshni Govender, Phumza Macanda and
Shapi Shacinda; Editing by Alison Williams)