The ANC's centenary birthday bash will cost more than R100- million, the party says.

"It is not cheap but we believe ... it is worth it. Future and younger generations need to know where we come from," ANC national chairman Baleka Mbete told reporters in Johannesburg.

The ANC was gathering information about its history from around the world to be housed in one place.

"Some of the work is just priceless," Mbete said.

"Friends" of the ANC were helping with funding.

About 120000 people were expected to attend the main 100-year birthday celebration in Mangaung in the Free State in January.

"We are now, as of today, 60 days away from the anticipated January celebration to commemorate the birth of the oldest surviving liberation movement in the continent."

Mbete said the ANC had been preparing for the celebrations for the past two years.

The main bash would start on January 6 and go on until January 8. It would start in Waaihoek, in the Western Cape, where the ANC was founded 100 years ago.

The weekend would include an inter-faith night vigil, an awards ceremony, a traditional cleansing and restoration ceremony, a centennial gala and the main celebration at Mangaung stadium.

ANC president Jacob Zuma was expected to deliver the centennial address at the stadium on January 8.

Many international guests were expected to attend.

"[They] will be given the opportunity to speak about their relationship with the ANC," said Mbete.

A number of African heads were scheduled to attend.