South African trade union launched a protest Monday against plans by the country's Sasol chemicals company to exclude white staff from a new employee share-ownership scheme.

Solidarity, which has mainly white members including 6,300 at Sasol, said employees of the company's Secunda plant southeast of Johannesburg would strike on Thursday.

The union contests "the company's staff share scheme that excludes white employees", saying that 89 percent of Solidarity members at the facility supported the walkout.

"Solidarity is also calling on South Africans not to fill their tanks at Sasol petrol stations this coming Wednesday in support of the Sasol employees," it added in a statement.

Solidarity said it began a low-intensity industrial action on Monday that would escalate over the next three weeks.

"This will be a clever strike. Our 6,300 members are highly trained employees of major strategic importance to Sasol. We intend to switch off a different section of Sasol each day," said Solidarity chief executive Dirk Hermann.

Sasol spokeswoman Matebello Motloung told AFP that the new share scheme was not part of employees' basic remuneration and was intended to empower members of previously disadvantaged communities.

"It primarily focuses on the inclusion of black employees and public shareholders," she said.

"Our intention is to create meaningful financial benefits for approximately 230,000 black public shareholders and qualifying employees, and to achieve 25 percent direct and indirect black ownership."

Sasol, which employs 31,000 people in 33 countries, confirmed that Solidarity had said it would strike over the dispute.

Kim Ludbrook / EPA

"We have activated contingency measures to minimise potential disruption," Motloung added.

The ruling African National Congress (ANC) party said it had noted the strike action "with concern".

"The ANC is deeply concerned about the racist overtones of this strike, which seeks to reverse the gains of our democracy," said ANC spokesman Pule Mabe in a statement.

"In characterising the Sasol initiative as racial exclusion is at best malicious - and at worst dishonest."

The government introduced policies in 2003 to economically empower black South Africans.