Croatia and Slovenia jointly built Krsko when they were federal units of the former Yugoslav nation during the 1980s, but the plant has been in dispute since 1998.
Slovenian power monopoly Eles stopped distributing electricity from Krsko to HEP because of unpaid bills and moved to freeze Croatia out by nationalising the power plant in July 1998.
A HEP official said on Monday the legal deadline for settling the issue was July this year and said HEP was going to file its settlement proposal this week or next.
The Slovene side will have three months to respond. Failure to respond will invoke international arbitration, in line with the European Energy Charter, the HEP official said.
