His resignation comes 69 days after the Federal and Provincial elections ended.
Deuba, who was elected Prime Minister in 2017, held three successful elections -- local, provincial and federal assemblies.
Earlier on Thursday, Oli, along with Chairman of the Maoist Center Pushpa Kamal Dahal Prachanda, met Bhandari, as the former claimed the top executive post on the basis of majority votes, the President Office said.
Oli will have to prove his majority in the House within 30 days.
The two communist parties UML (Unified Marxist-Leninist) and Maoist Centre has expedited their unification process which they announced in October 2017.
(Anil Giri can be contacted at email@example.com)
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