* Union says workers at Kumba to strike next week
* Kumba says yet to get strike notice, open to talks
* Northam strike enters fourth week
(Recasts with Kumba comments, adds shares)
By Olivia Kumwenda
JOHANNESBURG, Sept 27 (Reuters) - South Africa's Kumba Iron Ore said on Monday it was willing to hold fresh talks with the National Union of Mineworkers (NUM), which plans to a strike next week after pay rise talks collapsed.
The NUM said earlier on Monday that over 6,000 workers at Kumba, a unit of global miner Anglo American, would go on strike after rejecting the company's offer of wage increases between 7 percent and 9.5 percent on a two-year deal, depending on the worker's category.
The NUM is demanding pay rises of between 7.5 percent and 10 percent on a one-year deal.
"Our doors are always open for discussions," Kumba spokesman Gert Schoeman said when asked if the company would seek fresh talks to avert a strike.
South Africa, the continent's biggest economy, has been hit by a wave of strikes and strike threats, which have led to pay settlements well above inflation -- at 3.7 percent in July -- and raised fears that the cost of living will rise.
"The decision to go on strike has been taken at Kumba, and a seven-days notice was served that the strike would begin next Monday," NUM spokesman Lesiba Seshoka said.
But Schoeman said Kumba, the 10th-largest global iron ore producer, had not received a formal notice from the NUM.
The union said it would press ahead with strike plans despite a possibility of new wage negotiations.
"A strike cannot be averted on the basis that there may be talks. We cannot rely on just an indication," Seshoka said.
The union said last week the strike would affect Kumba's Sishen, Kolomela and Thabazimbi operations.
Meanwhile, a strike at Northam Platinum entered its fourth week after the workers rejected the company's revised wage offer last week, the union said.
About 80 percent of Northam's 6,800 employees at its Zondereinde mine in South Africa have been on strike since Sept. 5, shutting the entire operation and costing Northam 1,000 ounces per day in lost production of Platinum Group Metals (PGMs).
Northam, one of South Africa's smaller platinum producers, raised its offer to 9 percent last week from 8.5 percent, below NUM's demand of a 15 percent increment.
Kumba shares, which have gained about 15 percent so far this year, were 0.57 percent higher at 350 rand at 1313 GMT, lagging a nearly 1 percent rise in the JSE'S All-Share Index.
Shares in Northam Platinum were up 3 percent at 46.51 rand in Johannesburg.
(Editing by Jane Baird)