The final approval for Sharif's nomination will be made during a meeting of the PML-N's parliamentary committee before the start of the first session of the new National Assembly.
The PML-N is all set to form government after emerging the single largest party in the National Assembly during the May 11 general election.
The party won 126 of 272 directly elected seats in the lower house of parliament.
The PML-N will be allocated 32 reserved seats for women and five reserved seats for non-Muslims.
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This will give it 181 seats in the 342-member House, or 10 seats more than the 171 required for a simple majority.
The PML-N's strength in the National Assembly could increase further as several parties - including the PML-F, National People's Party and National Party - are expected to enter into an alliance with it.
The new Prime Minister will be formally elected during the first session of the new National Assembly, which is expected to be summoned on June 1.
Meanwhile, hectic consultations are continuing within the PML-N on selecting candidates for key portfolios like foreign affairs, finance, interior, defence and power.
Sources said PML-N chief Nawaz Sharif is initially expected to retain the foreign affairs and defence portfolios with himself.
Senior PML-N leader Chaudhry Nisar Ali Khan has expressed an interest in the foreign affairs portfolio but his candidature has been opposed by other leaders.