If the parties fail to form the consensus government, Yadav will ask them to form a majority government, the President's Office said in a statement.
The president's announcement came hours after the Nepali Congress elected its president Sushil Koirala as the party's leader in the Constituent Assembly, which also doubles as the parliament.
Koirala, 74, is set to become the next prime minister as the Nepali Congress emerged as the single largest party in the 601-seat assembly after it secured 196 seats in the November 19 polls.