An unprecedented deal by oil producers to curb supply to match demand prompted by the COVID-19 pandemic is set to depend partly on purchases by consumer countries for their strategic stocks on a scale not seen before.

OPEC+ partnered with other producers like the U.S. for an agreement that will result in the removal of a total of around 19.5 million barrels per day from the market.

Reuters reports officials and sources from OPEC+ states to indicate that the International Energy Agency (IEA), the energy watchdog for the world's most industrialised nations, may announce purchases of up to several million barrels per day to buoy the deal.

But the IEA has never before performed a coordinated stocks purchase and has no effective mandate to do so, said two industry sources familiar with the process.

"It's completely down to individual countries," one of the sources said.

The IEA has in the past announced coordinated stocks releases, like during U.S. hurricane Katrina and the war in Libya. But never purchases.

The IEA said it would publish its monthly report on Wednesday in which it would provide an update on the latest market developments.