The leader of the National Party which ruled South Africa from 1948 until last year withdrew a veiled threat to stop co-operating in the five-year transition from all-white rule to multi-racial democracy.
Mr de Klerk's comments came in a combative address to his first National Party congress since losing power. The speech seemed mainly intended to reverse what he said was his party's recent loss of support because of an overbearing closeness with Mr Mandela's ANC.
"They become rudely insulting ... we will not allow ourselves to be bullied or intimidated," Mr de Klerk told 1,500 cheering delegates in Johannesburg's World Trade Centre.
Friction between South Africa's two main parties was already high because of a dispute that reached the Cabinet on Wednesday about the processing in the last days of Mr de Klerk's government of 3,500 amnesty applications by South African policemen.
The Cabinet Secretary, Jakes Gerwel, of the ANC, said on Wednesday that the government had agreed that the police had not been indemnified and that amnesties offered to more than 11,000 militants of the liberation movements were a separate issue. But Mr de Klerk said his National Party had vigorously dissented in Cabinet and accused the ANC of double standards.Reuse content