South Africa's powerful labour union COSATU said on Thursday it would intensify strikes already planned for July if the Reserve Bank announces another increase in interest rates later in the day.

If the Reserve Bank increases again the repo rate either by half a percentage point or a full percentage point we will be left with no option but to intensify the strike that we are going to be embarking upon in July and August and the rolling mass action which will take us right up to the end of this year, COSATU General Secretary Zwelinzima Vavi told Reuters.

South Africa's rand hit its weakest level since April 1 on Wednesday, weakened by the country's gloomy growth and inflation outlook. By 0655 GMT, the rand was trading 0.34 percent weaker at 8.03 to the dollar.

COSATU, an ally of South Africa's ruling ANC, is an umbrella labour federation representing two million workers.

South African inflation jumped to a near 5-1/2-year high in April. Reserve Bank Governor Tito Mboweni is expected to increase the bank's repo rate by a full percentage point later on Thursday, according to a Reuters poll of 22 economists.

COSATU already said on Wednesday it planned to call a national strike next month to protest against job losses linked to the country's power crisis.

South Africa has suffered electricity shortages since the start of the year as power utility Eskom [ESCJ.UL] struggles to generate enough power to meet demand.

The power shortages have dented economic growth, which fell to a 6-1/2-year low of 2.1 percent, quarter-on-quarter, in the first three months of 2008, unnerved investors and heaped pressure on President Thabo Mbeki. (Reporting by Stella Mapenzauswa; Editing by Marius Bosch)

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