US Secretary of State Mike Pompeo said the White House believed Iran was responsible for the attack, labelling it a "campaign" of "escalating tension" by the Middle Eastern country and a threat to worldwide peace and security.
The US Navy sent a destroyer, the USS Bainbridge, to assist, said Cmdr.
Iran has repeatedly warned it would block the Strait of Hormuz if it can not sell its oil because of US sanctions.
Ilan Goldenberg, a former senior state department official said: "I've been saying for the past month that threat of war with Iran is overhyped".
An oil tanker is on fire in the sea of Oman.
"The crew told us something came flying at the ship, and they found a hole", Katada said.
A Saudi-led coalition which has been fighting the rebels it accuses of being Iranian proxies said Saudi air defences had intercepted a new rebel attack on a Saudi airport on Friday.
"The Iranians, in response to our maximum pressure, are practicing their own version of maximum pressure", he said. The Houthis also claimed an armed drone strike last month on Saudi oil pumping stations.
Iran has suspended its adherence to some obligations under the nuclear deal and Tehran has taken a strong stance with their Foreign Minister making provocative statements including telling the USA it "cannot expect to stay safe" after increasing sanctions.
"Suspicious doesn't begin to describe what likely transpired", he wrote on Twitter earlier on Thursday. He provided no evidence, gave no specifics about any plans and took no questions. Company president Yutaka Katada offered no evidence for his claim, which contradicts the U.S. military account.
In London, British Foreign Secretary Jeremy Hunt said the United Kingdom was taking the matter "extremely seriously" and that if Iran was involved, "it is a deeply unwise escalation which poses a real danger to the prospects of peace and stability in the region".
United Nations secretary-general Antonio Guterres strongly condemned the attacks, warning that the world can not afford "a major confrontation in the Gulf region".
About 25 miles off the coast of Iran, the Front Altair oil tanker is disabled and on fire.
The Norwegian-owned Front Altair ethanol tanker was hit by three explosions, according to the Norwegian Maritime Authority, and continued to burn late Thursday. A short time later, the Kokuka Courageous, loaded with methanol from Saudi Arabia and Qatar, also called for help.
There was no claim of responsibility for the blasts, which struck both tankers at the waterline.
The U.S. Navy rushed to assist the stricken vessels in the Gulf of Oman off the coast of Iran, including one that was set ablaze Thursday by an explosion.
The world's eyes are already firmly fixed on Iran this week, as Japanese Prime Minister Shinzo Abe is in Tehran for a state visit.
The Kokuka Courageous is now sailing toward the port of Khor Fakkan in the United Arab Emirates, with the crew having returned to the ship after evacuating because of the incident, Kokuka President Yutaka Katada told a press conference.
Despite the escalation in tensions, Pompeo signaled that the United States will continue to limit its policy to economic pressure, which leaves few options for additional measures. "Whoever is behind the attacks is no friend of Iran".
The White House said President Donald Trump had been briefed and the US Government would continue to assess the situation.
"Throughout the first half of this year, ongoing global trade tensions have escalated", OPEC said in the report.
The conflict has pushed 14 million people to the brink of starving to death.
When asked if the United States had shown any evidence to support its accusation that Iran was responsible, Al-Otaibi told reporters: "We didn't discuss any evidence".
"Japan is an important Asian country and if it wants to expand ties with Iran, it should show a firm stance, as other countries have done", Khamenei said. "Never threaten the United States again!"
The shipping lane is used to move one-fifth of the world's oil supply and is critical to the world's economy.
Nearly one-fifth of the world's oil exports - from Saudi Arabia, Iran, the United Arab Emirates (UAE), Kuwait and Iraq - is exported using this route.
Anything affecting the narrow passage ripples through global energy markets, raising the price of crude oil.
[O/R] Brent crude LCOc1 was down by 0.4 percent at $61.06 a barrel in early Asia trading.