ZAGREB, Croatia (AP) — Croatia will hold a presidential election on Dec. 29, Prime Minister Andrej Plenković announced Tuesday.

The government is expected on Thursday to formally schedule the vote. If no candidate wins an outright majority on Dec. 29, a runoff vote will take place two weeks later.

Incumbent populist President Zoran Milanović has said he will run for reelection. Milanović is backed by the opposition Social Democratic Party, while his main challenger is expected to be Dragan Primorac, a candidate of the governing conservatives.

Milanović and Plenković are bitter political rivals. Milanović opposes the Croatian government’s support for Ukraine, including the participation of Croatian troops in a NATO-led training mission for Ukrainian soldiers.

The conservative government was shaken this week by the arrest of Heath Minister Vili Beroš on suspicion of corruption in procurement deals for Croatian hospitals.

Other candidates from the left and right are also expected to join the presidential race.

Milanović, 58, had served as prime minister in the past, before winning the presidential election five years ago by beating incumbent Kolinda Grabar Kitarović.