Prime Minister Manmohan Singh is likely to be admitted to the All India Institute of Medical Sciences (AIIMS) on Friday. Sources say he will undergo heart surgery on Saturday. Doctors say there is no threat to the PM's life. The Prime Minister will need rest for three to four weeks, sources say. External Affairs Minister Pranab Mukherjee will preside over the Cabinet meetings in the Prime Minister's absence. Internal orders on Pranab's expanded duties are ready, sources add.