FW de Klerk, the last leader of apartheid-era South Africa and a co-recipient of the 1993 Nobel Peace Prize with Nelson Mandela, is to be fitted with a pacemaker after falling ill.
Former president Mr de Klerk, 77, felt dizzy after returning home from Europe on Sunday. He has suffered several similar spells of dizziness in recent weeks.
He will have a pacemaker implanted today to help his heart function and will spend the night in hospital.
He and his wife Elita previously announced they were suspending a working visit and holiday in Europe because Mr Mandela is critically ill.
Mr de Klerk and the anti-apartheid leader led negotiations that ended white racist rule.