"Under the agreement, oil exporting states will supply petroleum to a country that is facing a shortage at a lower price," said S. Pushpanathan, deputy secretary-general of the Association of Southeast Asian Nations (ASEAN).
"The high price of oil is not an issue now, but should there be a crisis in the future, ASEAN can provide self-help," he told AFP.
It was not immediately clear how large a price reduction the deal would involve, when it would kick in or who would administer the pact.
Pushpanathan said oil price volatility posed a challenge to sustainable economic growth in the 10 ASEAN member states.
The agreement would be signed at the bloc's annual summit in the Thai beach resort of Hua Hin, he added.
"Given that ASEAN is increasingly dependent on petroleum resources from outside the region, it is important for ASEAN member states to enhance the ability to respond to an energy emergency situation by ensuring the physical availability of oil," he said.
Oil prices have slumped since hitting a record high above 147 dollars in July, as the global economic slowdown has hammered world energy demand. Prices have recently fallen to near five-year lows.