(CNN) Italy's President is expected Monday to ask a former International Monetary Fund official to be interim prime minister after leading populist parties dropped out of a bid to form a government.

The move comes after the populist coalition's choice for prime minister, Giuseppe Conte , abandoned his attempt to form a government following President Sergio Mattarella's refusal to endorse his euroskeptic choice for finance minister.

Mattarella said he had agreed with all of Conte's other demands, but his choice for finance minister, Paolo Savona, was unacceptable because his appointment would alarm investors and have dangerous consequences for Italy's outstanding government debt.

Italy has not had a government since it went to the polls in March, the longest such period in the country's postwar history.

Mattarella has summoned Carlo Cottarelli, former director of fiscal affairs at the IMF, to discuss forming an interim government, as new elections seem increasingly inevitable.