Speaking at a press conference after signing Croatia's EU Accession Treaty together with President Ivo Josipovic, Kosor said she was sure "more than 60 per cent" of Croatian citizens would vote for the accession.

Kosor said she dedicated this day and big achievement to Croatian war veterans and their families. "Without them, there would be no free Croatia or negotiations or Accession Treaty."

For today's big success, she thanked all previous Croatian governments, parliament, ministries, the negotiating team, the mission in Brussels and everyone in the state administration who worked on Croatia's European integration for years.

Asked why she was not holding a news conference together with the president, Kosor said "the president has his programme and I have mine," adding that she had suggested that Josipovic co-sign the Accession Treaty.

Asked if Slovenian Prime Minister Borut Pahor's wink before signing the document was meant for her, Kosor said she "didn't see a wink but a smile."

"I'm grateful to Prime Minister Pahor for his political courage. Both he and I were held back in our countries and if it weren't for our courage, the negotiations would still be blocked."

Asked if she would join Croatia's new government in the EU accession referendum campaign, Kosor said "they will have it harder than we did... They were against the (border) arbitration agreement (with Slovenia) and some reforms regarding the fight against corruption and the judiciary. We will carry on with what we began and I think the worst thing in politics is to change position."

After the signing of the Accession Treaty with Croatia, EU leaders began their regular summit, which Croatia is attending as an observer. At the beginning of the summit, Croatia was represented by Josipovic, who then gave his seat to Kosor.