Valletta, Malta - UN Secretary General Ban Ki-Moon said Tuesday that he had urged Iranian President Mahmoud Ahmadinejad to make a balanced and constructive contribution to a racism conference, at which the Iranian leader triggered a walkout.

Ahmadinejad, who has a history of denying the Holocaust and who once called for Israel to be wiped off the map, used the platform of the Geneva meeting on Monday to launch a tirade against Israel, describing it as a "most cruel and repressive racist regime."

Speaking to the German Press Agency dpa during an official visit to Malta, the UN secretary general said: "What happened (on Monday) was very regrettable and deplorable. The conference to fight racism and racial discrimination was misused for political purpose by the Iranian president."

Ban revealed that he had a long bilateral meeting with Ahmadinejad before the Iranian president took to the podium.

"I appealed to him and urged him to have a balanced and constructive contribution to the conference ... What he did was out of the scope of the conference and beyond what the international community expected," he said.

Over 40 diplomats representing Western nations walked out of the hall as soon as Ahmadinejad began attacking Israel.

Nine countries, including the United States and Israel, had boycotted the conference over concerns about its fairness.

The UN Secretary General said it was wrong for some countries to opt out of the conference - whatever differences of opinion one might have it is always better to participate in discussion and aim for a compromise solution.

"Racial discrimination is too serious an issue. We need the whole international community to take part. All human beings were born equal. The purpose of this meeting was very important," Ban said.

The Secretary General said Ahmadinejad had been invited to speak first because he was the only head of state at the conference, although invitations had been issued to other heads of state. (dpa)