RIYADH, Saudi Arabia — To the annals of peculiar diplomatic and cultural moments, add Saturday’s ceremony opening the summit of the Organization of the Petroleum Exporting Countries.

After the chanting of an opening prayer from the Koran about God’s “sublime light that reflects on mankind,” the president of Venezuela, Hugo Chavez, took the stage, crossed himself, invoked Jesus, and launched into a 24-minute rallying cry to reenergize what he called OPEC’s “revolutionary” battle against “exploitation” and to do more to alleviate poverty.

Citing the oil cartel’s origins, Mr. Chavez said “OPEC should set itself up as a more active political agent, to demand more respect for our countries, to ask the more powerful nations of the world to stop threatening OPEC.”

But after Mr. Chavez spoke, Saudi Arabia’s King Abdullah said that “oil is a tool for construction and prosperity … and it should not be a means for disputes or serving whims.”

For the past four days, OPEC and Saudi officials have been trying to portray the oil cartel almost as a public service organization, scrutinizing figures on consumption and production to find a balance that would moderate wild swings in prices for the benefit of consumers and producers alike. “We are not using the oil we are selling to the world as a political weapon,” the secretary general of the OPEC, Abdullah al-Badri, said. “We have not used [it] in the past, nor will we use it in the future.”