An attack on Iraq will by met by a temporary suspension of output quotas in a bid to avert demand-driven price rises, according to an OPEC source.
After two OPEC output hikes this year, only Saudi Arabia and perhaps United Arab Emirates have the capacity to make more supply available to world markets immediately.
"One or two countries could volunteer to make up for the loss of supplies should war start on Iraq [the world's eighth-largest oil exporter] but they would need the blessing of other members," the source said.
"It would be a temporary exemption, just as long as it takes to compensate for the loss and to cool off the market," he added.
The Organization of the Petroleum Exporting Countries, which is due to hold a policy meeting on March 11th, is already raising output to cover for an unexpected cut in strike-hit Venezuela. It would be pushed to full capacity if Iraqi production also stops.
After the presumed war, the source said OPEC would return to the current production ceiling of 24.5 million barrels per day (bpd).
If war has not broken out before OPEC ministers meet, the source said the cartel would probably make no change in the 24.5 million bpd ceiling.
"Until war starts, there is nothing more they can do. More production can't cool prices. They are high because of war hysteria," the source said.
Oil industry analysts estimate that Saudi Arabia and UAE combined have about two million barrels per day (bpd) of spare oil output capacity, roughly equivalent to Iraq's current exports.