Pakistan has asked for more time to decide on the issue and may instead choose to send a representative, CNN-IBN reported.
According to NDTV, the ministry of external affairs has begun the procedure by sending in invites to the leaders of SAARC countries as well as other world dignitaries.
The decision to invite heads of SAARC as well as non-SAARC countries was taken by the new leadership on Tuesday. Delhi Police, which will have to oversee the security arrangements, have also been informed regarding the decision on Wednesday.
Modi will be administered the oath of office by President Pranab Mukherjee in the forecourt of Rashtrapati Bhavan at 6pm.
At least 3,000 dignitaries will be invited to attend the ceremony.
Sharif had formally invited Modi to visit Pakistan soon after the BJP emerged as the clear winner in the Lok Sabha elections.
The BJP had a landslide victory in the just-concluded polls to elect members for the 16th Lok Sabha. The party won more than 272 seats in the 543-member House on its own.
(With agencies input)