HSS leader Josip Friscic said the coalition intended to win at least 21-25 seats in the parliament.
The three parties are open to cooperation with other parties and expect to be joined by some leading regional parties, he said.
The parties also signed a 10-point election platform, including goals such as decentralisation, promoting a business climate, protecting national resources and interests, protecting ethnic minorities, etc.
Asked to comment on the HSS-HSLS-PGS coalition agreement, PM Ivo Sanader said that the HSS-HSLS agreement was a good move of the two centrist parties.
Sanader said that his party, the Croatian Democratic Union, was negotiating with all parties and that talks could soon be held with Opposition representatives.
This is an election year, but some issues should not be neglected, notably talks with the EU, Sanader said, expressing hope that parties would put aside their individual interests and cooperation on issues related to Croatia's integration with the EU and NATO.