JOHANNESBURG, July 8 (Reuters) - South Africa's striking NUMSA union said on Tuesday it would take the latest offer from the main employers' group to its members on Wednesday, possibly ending a week-old stoppage that has hit car manufacturers.

A spokesman for the engineering and metal workers' union did not elaborate on the offer. The labour ministry said the two sides were "very close" to securing a deal.

"The differences are in terms of fractions," ministry spokesman Mokgadi Pela told Reuters.

Pretoria has intervened to try to break a deadlock that is costing industry an estimated 300 million rand ($28 million) a day.

Africa's most advanced economy is struggling to recover from a series of work stoppages that have eroded business confidence.

The strike by more than 200,000 NUMSA members, asking for increases of between 12 to 15 percent, follows a crippling walkout by platinum miners that lasted five months.

The mining strike ended two weeks ago when the country's top three platinum producers struck a deal with the Association of Mineworkers and Construction Union (AMCU) to increase wages by about 20 percent.

"TIME BOMB"

Separately, the National Union of Mineworkers (NUM) warned on Tuesday that state-owned power utility Eskom was "sitting on a time bomb" for not allowing employees to strike, signalling workers there might embark on an unofficial stoppage.

Industrial action at Eskom, which provides 95 percent of the power to Africa's biggest economy, could force plants such as smelters, mines and factories to shut down.

The NUM, which represents around 16,000 workers at Eskom, has already rejected a 5.6 percent wage offer and is demanding 12 percent.

"If doctors can strike in South Africa, why can't Eskom workers strike?" NUM General Secretary Frans Baleni told a news conference.

"Our members are angry. Eskom is sitting on a time bomb."

Baleni said the workers, who are not allowed to strike as they are deemed to provide an essential service, were angry, adding the union would not stop a wildcat strike.

"Anything is possible at Eskom. If workers decide to react in various forms including an unprotected strike, we cannot be blamed," he said.

Last month's wage settlement in the platinum belt ignited a separate wildcat strike by 2,000 NUM-affiliated workers at Impala Platinum's Marula mine on Friday.

But those miners are now back to work and negotiations have started on their demands that Implats match the deal obtained by AMCU in other platinum mines.

"They are all back to work. We are now engaging with them about their concerns," Implats spokeswoman Alice Lourens said.

• [Editor:Juan]