Stock futures tumbled after hours on Wednesday, building on earlier losses for the S&P 500 and Dow Jones Industrial Average, as crude-oil prices pressed higher.

Oil futures posted double-digit declines amid some optimism that the war in the Middle East could end sooner than previously thought, and G-7 finance ministers considered a possible release of oil from strategic reserves.

U.S. stock index futures were subdued Wednesday as investors assessed the outlook for crude prices and looked ahead to a key inflation report.

Oil fell for the first time in six days as the U.S. government mooted interventions in the futures market and waived Indian purchases of Russian crude.

U.S. oil futures added about $6 a barrel in late trading after the Energy Department said it will tap the Strategic Petroleum Reserve in conjunction with similar market-supporting moves announced earlier by allies including Germany and Japan.

A shaky start to the week is in store for financial markets after the U.S. and Israel attacked Iran over the weekend.

Futures rose amid a reported plan for a record release of crude oil reserves. Oracle jumped on earnings late.

Futures tied to Canada's main stock index dipped on Wednesday as investors monitored the latest developments in the Iran war, ​while awaiting key U.S. inflation data due later in the ‌day.