Concerns of energy and food supply security will take centre stage in two days of meetings by leaders and ministers of the bloc of 11 nations, home to nearly 700 million, that is among the regions most exposed to fallout from the conflict.
The event's chair, the Philippines, hopes ASEAN ministers can hammer out an oil-sharing framework agreement at special meetings held before the summit.
"ASEAN needs to strengthen our crisis co-ordination and institutional readiness in times of crisis," said Theresa Lazaro, the Philippine foreign affairs secretary.
"The ongoing crisis in the Middle East and its far-reaching repercussions ... remind us that developments beyond our region can have immediate and profound effects on ASEAN," she said on Thursday before a meeting with counterparts.
Diplomats and analysts say the energy issue will prove a test of the Philippines' skills as chair, forcing it to shape a regional response while preventing ASEAN's own conflicts slipping down the agenda.
These include Myanmar's civil war and 2025's deadly and still unresolved border dispute between Thailand and Cambodia, despite an uneasy calm after a ceasefire.
The Philippines arranged a three-way meeting of President Ferdinand Marcos Jr and the leaders of Thailand and Cambodia later on Thursday.
Thailand and Cambodia have stuck to the ceasefire since late December, following two eruptions of fighting along stretches of their 800km border, the first of which ended after intervention by US President Donald Trump.
ASEAN, with a combined gross domestic product of about $US3.8 trillion, has long struggled to coordinate its responses to crises, with meetings typically resulting in pacts to co-operate, rather than a clear strategy or concrete commitments.
However, the scale of the energy supply shock was likely to push the bloc beyond rhetoric, as no ASEAN country could escape the issue, former Philippine diplomat Laura del Rosario said.
ASEAN leaders are set to call for good-faith negotiations between the United States and Iran and a halt in hostilities, according to a working draft of a statement seen by Reuters.
It also called for international law to be upheld and traffic to flow unimpeded through the vital Strait of Hormuz, usually a conduit for a fifth of the world's oil and gas supplies.
They will also consider the crisis in Myanmar, which has divided the bloc.
The nation's new, nominally civilian government is keen to re-engage with ASEAN after an election swept by a party backed by the military, which had ruled for five years since a 2021 coup.
ASEAN has not recognised the election or said when the leaders of Myanmar, whose president Min Aung Hlaing is the former junta chief, can return to its summits after five years on the sidelines.
