ATHENS, Greece (AP) _ Iran's president appealed Thursday for world leaders to use the ``power of dialogue'' to prevent religious and cultural differences from turning into conflict.

Mohammad Khatami steered clear of direct references to Middle East violence or Iran's unrelenting tensions with Washington. He urged policy-makers to learn from the wisdom of ancient philosophers and the mistakes of past wars.

``Today, as yesterday, we have to acquire the power of dialogue with others,'' Khatami told an audience at Panteion University in Athens. ``It is only through this that we can explore the boundaries of our knowledge and ... create peace and security.''

Khatami said such efforts could be led by nations such as Iran and Greece, which he called important contributors to the ``ancient book of civilization.''

Khatami, who toured the Acropolis earlier Thursday, was the sponsor of a U.N. peace forum called ``Dialogue among Civilizations.''

The first stage of his visit to Greece concentrated on business. On Wednesday, Greece and Iran promised to explore ways to extend an Iranian natural gas pipeline from Turkey to Greece. The link could open new European markets for Iran, which has the world's second-largest natural gas reserves.

Khatami, who arrived from Austria, also repeated his strong denunciations of U.S. government policies he called aggressive and destabilizing. U.S. President George W. Bush had labeled Iran part of an ``axis of evil'' along with Iraq and North Korea.

Khatami plans talks with Greek political and religious leaders before returning to Iran on Friday.