On Monday, Seks is scheduled to hold talks with Ukrainian President Viktor Yushchenko and acting Foreign Minister Boris Tarasyuk.
The Croatian parliament speaker will also visit the ANTK Antonov factory.
Ukrainian Parliament Speaker Volodymyr Lytvyn visited Croatia in September 2005 when Seks and Lytvyn discussed the two countries' parliamentary cooperation which they agreed must be more systematic and broader.
The two officials agreed that Croatia-Ukraine relations are not hampered by any outstanding issues and that the excellent bilateral relations should be intensified at the level of parliaments, governments and presidents of state.
Lytvyn said Ukraine was interested in Croatia's experience in solving problems in home and foreign affairs, notably its experience in transforming from a presidential into a parliamentary system and its activities in the process of joining the European Union.
Seks stressed he and Lytvyn were agreed that both parliaments should adopt declarations on parliamentary cooperation to improve the quality of bilateral relations.
On that occasion, the leaders of the two parliaments signed a memorandum on parliamentary cooperation aimed at the strengthening of parliamentary relations and the exchange of experience. The document also supports the exchange of parliamentary visits.