Energy prices have jumped after Iran responded to an Israeli attack on a major gas field by hitting Qatar's Ras Laffan Industrial City, which processes around a fifth of the world's liquefied natural gas, causing damage that will take years to repair.
Saudi Arabia's main port on the Red Sea, where it has been able to divert some exports to avoid Iran's closure of the Gulf's exit point, the Strait of Hormuz, was also attacked.
US President Donald Trump said he had told Israeli Prime Minister Benjamin Netanyahu not to repeat the attack on energy infrastructure.
"I told him, 'Don't do that', and he won't do that," Trump told reporters in the Oval Office, where he met Japanese Prime Minister Sanae Takaichi.
A US official and three other people familiar with the planning told Reuters that Trump was considering sending thousands more troops to the Middle East. But at his meeting with Takaichi, Trump said he had no plans to deploy ground forces.
"I'm not putting troops anywhere," he said.
Three Israeli officials said Israel's bombing of Iran's South Pars gas field had taken place in consultation with the United States, but was unlikely to be repeated. Trump said the US had not known about it.
Netanyahu, in a press conference later, said Israel acted alone in the bombing of the South Pars gas field and confirmed Trump asked Israel to hold off on such attacks.
Iran is being "decimated" and no longer has the capacity to enrich uranium or make ballistic missiles after 20 days of US-Israeli air attacks, but a revolution in the country would not come from the air and would require a "ground component", he said, without elaborating.
Britain, France, Germany, Italy, the Netherlands and Japan issued a joint statement expressing "our readiness to contribute to appropriate efforts to ensure safe passage through the Strait".
They also promised "other steps to stabilise energy markets, including working with certain producing nations to increase output".
German Chancellor Friedrich Merz reiterated that any contribution to securing the strait would come only after hostilities ended.
Earlier, US Defence Secretary Pete Hegseth told a briefing that American objectives in the war, which has so far killed more than 2000 people, mostly in Iran and Lebanon, were "unchanged, on target and on plan".
Director of National Intelligence Tulsi Gabbard told a US congressional committee that American and Israeli goals differed.
The Israeli government had been focused on disabling the Iranian leadership, Gabbard said.
"The president has stated that his objectives are to destroy Iran's ballistic missiles launching capability, their ballistic missile production capability, and their navy."
The Trump administration is requesting $US200 billion ($A282 billion) of additional funding for the war, a US official confirmed on Thursday, but the request faces stiff opposition in Congress, which must approve the funds.
Iran's military said strikes on Iran's energy infrastructure had led to "a new stage in the war" in which it had attacked energy facilities linked to the United States.
"If strikes (on Iran's energy facilities) happen again, further attacks on your energy infrastructure and that of your allies will not stop until it is completely destroyed," spokesman Ebrahim Zolfaqari said, according to state media.
Israeli media reported an Iranian strike hit oil facilities in Israel's port of Haifa, causing damage but no casualties.
Since Wednesday, Iranian attacks have also forced the UAE to shut its Habshan gas facility and set off fires at two Kuwaiti oil refineries.
Brent crude oil futures were up nearly three per cent at $US110.35, having surged up to 10 per cent before the joint statement from European nations and Japan.
