Online registration for the event, which includes two long trails - the 20-kilometre Gospic Tesla trail and the 34-kilometre Otocac Gacka trail, is possible until August 28.
The head of the county tourism board, Ivan Radosevic, said interest in the event was great and that participants were mostly from Zagreb and Zadar as well as other parts of the country.
Additional mini trails have been introduced due to inquiries by a large number of people with small children.
Radosevic said that the event would be officially included in the International March Association calendar of events in 2019.
He said that the region of Lika boasted a beautiful, almost pristine nature and that on September 1-2 the weather was expected to be good.