Israeli leader Ariel Sharon will officially hand charge to his deputy, Ehud Olmert, when he undergoes an operation to plug a hole in his heart.
Mr Sharon will be incapacitated for about three hours
The prime minister's office said Mr Olmert will be head of government for roughly three hours on Thursday, while Mr Sharon is being operated upon.
Mr Sharon will be unconscious during the procedure, decided on following a minor stroke he suffered in December.
The prime minister is leading a new centrist party to the polls in March.
Early results show that Mr Sharon's Kadima party, which he formed by severing a decades-old alliance with the ruling Likud party, could fare well in the forthcoming elections.
'No lasting damage'
Doctors have said Mr Sharon's stroke may have been the result of a blood clot caused by a 2mm hole in his heart.
An umbrella-like device will be inserted through a small tube passing along a blood vessel in order to plug the hole, doctors said.
During the operation and the recovery period, Mr Sharon's authority "would be transferred to Acting Prime Minister Ehud Olmert", according to a statement from Mr Sharon's office.
The Israeli leader is expected to be in hospital for 24 hours.
Doctors say he suffered no lasting damage from the stroke and that his blood pressure and cholesterol levels are normal.
However, he has been advised to reduce his workload and avoid eating fatty foods.