The US military has released a video it says shows Iran's military removing an unexploded mine from one of the two oil tankers attacked in the Gulf of Oman.
US President Donald Trump has publicly accused Iran of being behind the attacks, describing them as a "nation of terror".
The footage, as well as still images released by the US military's Central Command, appeared to show a limpet mine on the Kokuka Courageous.
An Iranian Revolutionary Guard patrol boat then pulled alongside the ship and removed the mine, according to the command's spokesman Captain Bill Urban.
Captain Urban also said: "The US and the international community stand ready to defend our interests, including the freedom of navigation.
"The United States has no interest in engaging in a new conflict in the Middle East. However, we will defend our interests."
The US Navy's USS Bainbridge rushed to assist the vessels, which were damaged 25 miles off the Iranian coast.
Warship USS Mason has also been sent to scene to assist.
US Secretary of State, Mike Pompeo, said the images proved Iran was "responsible" for the attack.
He said the conclusion was reached through intelligence, the weapons used and how "no proxy group operating in the area" can work with "such a high degree of sophistication".
Mr Pompeo also mentioned there were "recent similar Iranian attacks on shipping".
Hamish de Bretton-Gordon, a weapons expert, said the "American's will expect our full moral support" as we are close allies.
"We work very closely with the Americans in this part of the Gulf and the Middle East and we have a significant naval base in Bahrain," Mr de Bretton-Gordon said.
"I expect it will be us supporting [the US] with our intelligence assets.
"I do not see that we would put any British fighters or British missiles into any assault," he added.
This incident comes just a month after four oil tankers were attacked nearby, off the coast of the United Arab Emirates.
The United States also accused Iran who denied being involved.
In the latest attack, Iran has also denied involvement, calling it an "unfounded claim" in the US' "Iranophobic campaign".
It also told the UN it condemns the allegation "in the strongest possible terms".
Meanwhile, Foreign Secretary Jeremy Hunt has said Britain backs the US' assessment.
He warned if Iran was proven to be behind the incident, it would be a "deeply unwise escalation which poses a real danger to the prospects of peace and stability in the region".
Tensions between the US and Iran have been rising since President Donald Trump pulled out of the 2015 nuclear deal.
The US recently sent an aircraft carrier and bombers to the Persian Gulf, to counter what it said was a growing threat from Iran.