Croatian Prime Minister Ivo Sanader on Wednesday announced his sudden resignation from the post of the government head and would not explain clearly the reasons for his decision.

Sanader, who is president of the senior ruling party Croatian Democratic Union (HDZ), told an extraordinary news conference that he also decided to withdraw from his party duty and from active politics and become HDZ honorary president, the Croatian news agency HINA reported.

Sanader said he had made the decision after deep consideration, and recalled that he had been in politics 20 years, and at the helm of the HDZ for 10 years. He said he would not run for president of the country later this year, and dismissed speculation that he is ill.

Sanader said he had informed Croatian President Stjepan Mesic of his decision on the phone. Sanader said that he had notified the presidents of the ruling coalition parties about his decision, that they accepted it, and that the coalition would survive in parliament.

"We already have 83 signatures of support from our coalition partners, which are the majority as it is," he said, adding the coalition would nominate Deputy Prime Minister Jadranka Kosor as the new prime minister.

Kosor is likely to succeed Sanader also as president of the HDZ.

The Croatian government, consisting of a coalition of the HDZ, the Peasant Party, the Social Liberals and representatives of ethnic minorities, is deemed to have resigned with the resignation tendered by Sanader.

Under the Croatian law on the government, the prime minister forwards his resignation to the parliament and if the highest law-making body accepts the resignation, it will dissolve the cabinet of the resigning prime minister.

According to the make-up of the parliament and consultations conducted, the head of state should then nominate a person who enjoys the confidence of a majority of MPs as new prime-minister designate.

If within 30 days a vote of confidence is not passed for the new premier-designate and the candidates for new ministers, the parliament speaker shall inform the president who should then decide on the dissolution of the parliament and on calling early parliamentary elections.

Asked by the press if he was ruling out any possibility of becoming active in politics in the future, Sanader said he could not rule this out, and dismissed allegations that he was stepping down because of the difficult situation Croatia is in.

Responding to repeated questions from the press to explain in more detail reasons for his withdrawal, Sanader said he had done his part of the job.

"In life there are moments for a fresh start and I have come to the conclusion that this is one of those moments. I did my share, and now it is time for others," Sanader said.

"I am leaving satisfied as all strategic goals have been achieved. Croatia has become a true factor of the international politics, we are a member of the Security Council, NATO and we are on the threshold of the European Union, only a political decision needs to be made and we can finish negotiations in three months' time," he said.

Following a meeting with Sanader on Wednesday evening, President Mesic said in a statement that he had taken note of Sanader's decision to resign, stressing he was surprised by Sanader's choice of the moment to announce his decision.