Sharif and Karzai are among the leaders who have been extended verbal invitation and Karzai has already accepted the same, sources said.
This will be followed by written invitation, they said.
However, there was no clarity on who all have been invited for the swearing-in ceremony at the forecourt of the historic Rashtrapati Bhavan here which will be attended by over 3000 guests.
Modi will be administered the oath as 15th Prime Minister of the country by President Pranab Mukherjee. BJP had a landslide victory in the just-concluded polls to elect members of the 16th Lok Sabha and crossed the majority mark of 272 in the 543-member House on its own for the first time in its history.