Asian refiners are moving earlier than usual to secure crude oil from Russia’s Far East, as hopes for a swift resolution to Middle Eastern supply disruptions fade and the expiration of a U.S. temporary waiver on Russian oil looms.

Cargoes of Eastern Siberia-Pacific Ocean blended crude oil—a light, sweet Russian grade exported from the Kozmino terminal in the Far East to Asia-Pacific markets—are normally traded one month before loading. But with the Strait of Hormuz effectively closed, trading has kicked off early as refiners rush to plug supply gaps, according to Kpler.

“The unusually early start to Russian crude trading underscores the urgency among Asian refiners to secure supplies as hopes for a swift restoration of Middle Eastern flows fade,” said Muyu Xu, senior crude analyst at the data provider.

Earlier this month, the U.S. said it would temporarily allow countries to purchase Russian oil already at sea in an effort to boost supply and ease pressure on crude prices. The waiver runs through April 11.

After receiving the U.S. green light, Indian refiners quickly purchased significant volumes of Russian Urals crude and some Russian Far East barrels for March and April arrivals, according to Kpler data. Other Asian buyers, including Chinese state-owned refiner Sinopec, have moved early to lock in shipments for May.

“Prompt Russian crude availability is tightening, with floating storage dropping sharply and most May cargoes likely already committed,” said Xu. Kpler estimates Russia’s exports at around 3.9 million barrels a day so far in March, compared with 3.2 million barrels a day in February.

Strong Asian demand led by India and China is also driving a sharp rebound in Far East crude premiums, though the grade remains competitively priced versus other supplies. Prices for May shipments are now estimated at around $10 per barrel above Brent crude, Kpler said, though exact pricing remains unconfirmed.

Write to Giulia Petroni at giulia.petroni@wsj.com