Simonovic said in an interview with Reuters on Thursday that delays could weaken support for the Croatian government and lead to possible instability in the Balkans.
"Europe is a dream. (Some would say) if it is not realistic, let's get back to our nationalist agenda. In Bosnia and Serbia, this is a serious threat," said Simonovic, who will soon leave his ministerial post to take office as UN Assistant Secretary-General for Human Rights.
"In Croatia, I wouldn't say the danger is the same. But if there is no success in finishing negotiations this year, it would substantially contribute to instability of the government," he said.
"We have an unspoken consensus in Croatia (that) this government is leading us through EU negotiations so we should all support it ... If negotiations are not moving, all the bitterness related to the economic situation can rise."