Wall Street futures were mixed early Wednesday while oil prices stabilized after President Donald Trump said the US Navy may escort tankers through the Strait of Hormuz, where about a fifth of the world's oil passes.
Futures for the S&P 500 fell 0.1% before the bell and futures for the Dow Jones Industrial Average slipped 0.2%. Nasdaq futures were essentially unchanged. Oil prices are up about 11% since the United States and Israel launched an attack on Iran five days ago.
On Tuesday, Trump announced that he had ordered the US Development Finance Corp. to provide political risk insurance and guarantees for financial security of all maritime trade.
"If necessary, the United States Navy will begin escorting tankers through the Strait of Hormuz, as soon as possible," Trump said in a social media message posted by the White House.
The price of US benchmark crude oil fell slightly to $73.94 per barrel early Wednesday. Brent crude, the international standard, gave up 37 cents and fell to $81.03 per barrel.
"Trump's assurances of the US underwrite shipping insurance against Middle East conflict risks and even US naval escorts only mitigate, but do not eliminate, enduring upside risks to oil prices," Mizuho Bank said in a commentary.
The increased insurance costs filtering through to shipping would ultimately cost an extra $5 to $15 a barrel, it said, adding that the "'war premium' remains firmly intact."
Worries over the war, which Trump has suggested could last a month or longer, have hammered world markets, unsettling investors who fear more spikes for oil prices may grind down the global economy and sap corporate profits.
"I think the Iran situation is getting out of hand, and I think that US President Donald Trump miscalculated enormously," said Francis Lun, CEO of Venturesmart Asia. "The situation is very grim."
Some analysts say stocks could rebound if the war ends soon. If it drags on, higher inflation partly due to rising energy prices could tie the Federal Reserve's hands and keep it from cutting interest rates.
For now, one of the most evident impacts on the economy has been a surge in gasoline prices.
The price for a gallon of gasoline is rising sharply in the US, up 22 cents from just last week, according to motor club AAA on Wednesday. Gas prices were already rising before the US launched strikes on Iran as refiners were switching over to summer blends of fuel.
Market sentiment appeared to brighten early Wednesday in Europe, where Germany's DAX climbed 1.3% and the CAC 40 in Paris rose nearly 1%. Britain's FTSE 100 was 0.8% higher.
In Asia, South Korea's Kospi led the regional losses as energy security concerns eclipsed optimism over the boost computer chipmakers like Samsung Electronics and SK Hynix have been getting from expanding use of artificial intelligence.
The Kospi sank 12.1% to 5,093.54. Samsung's shares dropped 11.7%, while SK Hynix gave back 9.6%.
The Korea Exchange temporarily halted trading for the Kospi index, while a circuit breaker was also triggered on the tech-oriented Kosdaq after it fell by more than 8%. It later dropped nearly 14%.
South Korea's stock market has been one of the world's best performers this year, but its economy depends heavily on trade and fuel imports, that are threatened with disruptions to traffic through the Strait of Hormuz, the narrow gateway to the Persian Gulf through which roughly a fifth of globally traded oil passes.
In Tokyo, the Nikkei 225 shed 3.6% to 54,245.54. Like South Korea and Taiwan, Japan depends heavily on imports of oil and natural gas from the Persian Gulf.
Elsewhere in Asia, the Hang Seng in Hong Kong fell 2% to 25,249.48 and the Shanghai Composite index shed 1% to 4,082.47.
In Australia, the S&P/ASX 200 declined 1.9% to 8,901.20.
Taiwan's Taiex lost 4.4% and shares in Bangkok sank 6%.
The price of gold rose 1.2%, while silver gained 2.6%.