The decision to red-list Croatia will formally be made at Thursday's cabinet session and published in the Official Gazette the same day.

"Fact is that the situation in Croatia is deteriorating dramatically. Data on infections show that the situation is really bad," Kacin said after the government meet epidemiologists to discuss the way forward.

He said Croatia was likely to today exceed 40 new cases per 100,000 inhabitants in over a 14-day period, the threshold in Slovenia for putting countries on the red list.

"We don't have any other choice but to urge our citizens to return from the dangerous country as soon as possible, regardless of what kind of arrangements they have. The situation is deteriorating rapidly and will get much worse," he said.

The decision comes after the Slovenian government started issuing increasingly stern warnings to Slovenian holidaymakers in Croatia that the situation was getting out of hand, in particular due to beach parties at several popular tourist resorts in Dalmatia.

Almost half the new cases Slovenia registered on Monday were imported from Croatia, and most of the infected persons are young, under 35.