"Unfortunately, some states in the Arab and Islamic region tolerate or support this rare genocide with silence or a smile of satisfaction," Ahmadinejad said in a letter to Saudi King Abdullah, referring to the Israeli operation in Gaza.
"Your Excellency, the king of Saudi Arabia and the custodian of the two holy mosques.., it is expected from you to break the silence over this obvious atrocity and killing of your own children," Ahmadinejad said in the letter, carried on his website.
Israel's 20-day old Gaza offensive has left more than 1,000 Palestinians dead and around 5,000 wounded, according to Gaza medics.
Ahmadinejad said he hopes that the Saudi king's stance "will fully disappoint corrupt powers that hope to create division in the Islamic front."
He was apparently referring to a rift between the so-called "moderate" Arab countries, led by Egypt and Saudi Arabia, and the more pro-Hamas states, led by Syria and Qatar, over how to respond to the Gaza assault.
Qatar has tried twice to organise an Arab summit on the Gaza conflict, an idea opposed by regional heavyweights Egypt and Saudi Arabia.
The letter to the Saudi king was released as Riyadh was set to host an emergency summit of the Gulf Cooperation Council on the situation in Gaza on Thursday.
Besides Saudi Arabia, the GCC also comprises the United Arab Emirates, Kuwait, Bahrain, Qatar and Oman.
