As Saudi Arabia prepares to host a summit of oil producers and consumers Sunday, it finds itself without its usual leverage over oil markets. Concerned about the long-term impact of soaring prices, Saudi Arabia is limited in its ability to do much about it.

The world's largest oil supplier does have two blunt weapons in its arsenal if it wants to try to beat down soaring oil prices to assuage the growing outcry over pump prices in world capitals. It can open its spigots wider to put more crude on the market, and it can sharply...