The US blamed Iran for the fatal attack on an Israeli tanker off the coast of Oman and promised an “appropriate response”.
The MT Mercer Street tanker was hit in the northern Indian Ocean on Thursday, killing two crew members in what the US said was a drone strike.
“After examining the available information, we believe that Iran carried out this attack,” US Secretary of State Anthony Blinken said in a statement, adding that the attack was carried out with the help of a drone.
“We are working closely with our partners to review next steps and are consulting with governments in the region and beyond to find an appropriate response ahead of time,” Blinken added.
Britain also said it believes Iran carried out the attack deliberately in “a clear violation of international law”.
On Sunday, Iran denied involvement in the attack, and Foreign Ministry spokesman Saeed Hatibzadeh said Israel should “stop such baseless accusations”.
“Iran will not hesitate for a moment to defend its interests and national security,” he told a news conference.