ATHENS Greek Prime Minister Kyriakos Mitsotakis was due on Monday to receive an official mandate to try form a coalition government after falling short of an absolute majority win in Sunday's election.

Mitsotakis' New Democracy party won 40.8% of the vote versus 20% for the leftist Syriza.

The result was a stunning boost for Mitsotakis, whose administration had to deal with a wiretapping scandal, the COVID pandemic, a cost of living crisis and a deadly rail crash in February which triggered public outrage.

But under a new voting system, he failed to win outright, getting 146 seats in the 300-member parliament, below a threshold of 151 lawmakers to govern the country alone.

Greek President Katerina Sakellaropoulou was expected to invite Mitsotakis on Monday and hand him a three-day mandate to lead negotiations with other parties to try to form a coalition.

If the talks fail, the second and third parties - Syriza followed by the socialist PASOK - each get a three-day mandate as well.

Should no party succeed in forming a coalition, Sakellaropoulou will appoint a caretaker government to take the country to a new vote about a month later.

On Sunday, Mitsotakis said that people gave him the mandate to "rule strong and autonomous", suggesting he was unlikely to join forces with any other party.

His sights were set on the second ballot which will take place under a semi-proportional representation, with a sliding scale seat bonus, increasing the chances of an outright win for his party.

"The dynamics of the result were more than clear: citizens want a strong government, with a four-year term, (to carry out) bolder reforms," Mitsotakis said after his win on Sunday.

(Reporting by Karolina Tagaris and Angeliki Koutantou; Editing by Raju Gopalakrishnan)