RIYADH, Saudi Arabia — Saudi Arabia’s king urged a gathering of Muslim scholars yesterday to open religious dialogue with Christians and Jews. But politics intruded as a senior Iranian figure said the Islamic world should stand up to America and its “international arrogance.”

King Abdullah spoke at the start of a three-day conference of Islamic scholars, clerics, and other figures in the holy city of Mecca called to get Muslims on the same page before the kingdom launches a landmark initiative for talks with adherents of other monotheistic faiths.

The tone was one of reconciliation between Islam’s two main branches, Sunni and Shiite. Mr. Abdullah, one of Sunni Islam’s most prominent figures, entered the hall with a Shiite Iranian politician, Akbar Hashemi Rafsanjani, who later sat at the king’s left in a gesture of unity.

But while Mr. Rafsanjani spoke warmly of his host, he also highlighted the political divide between their nations by delivering pointed criticism of America, a Saudi ally. Saudi Arabia has presented its dialogue proposal as a strictly religious initiative — an opportunity to ease tensions within Islam and between it and Christianity and Judaism.