The agreement, signed by Zvonimir Sabati of the HSS and Miroslav Korenika of the SDP, says that the two parties will participate in the local elections on a joint platform and will nominate a joint candidate for head of the county.
Korenika said that the coalition of the two parties would be the strongest in the county and that they expected to rule together.
"This agreement is also important for the next parliamentary elections, and we expect them to be held ahead of schedule," Korenika said.
The two parties said they would try to nominate joint candidates in as many towns and municipalities as possible, and added that they were also open to cooperation with other parties and non-governmental organisations.
They said that their joint activities would contribute to strengthening local self-government.