The government has long planned to sell a 51 percent stake in state-run PSO, together with the management control, but the auction has been repeatedly postponed due to lukewarm interest.
Previously, two bidders, Kuwait Petroleum Corp and Fauji Foundation, expressed interest in buying PSO.
The new call for expressions of interest is apparently aimed at attracting other potential buyers.
The statement quoted Privatisation and Investment Minister Abdul Hafeez Sheikh as saying that he expected interest from around the globe that would give impetus to the government's privatisation programme.
The statement said the parties that had earlier shown interest had been asked to reiterate their interest.
The US investment firm J.P. Morgan is the financial adviser for the sale.