Foreign ministers from the Group of Seven wealthy economies said that all available evidence showed Iran was behind an attack on the Mercer Street tanker last week, Reuters reported.
The group slammed the country for threatening international peace and security.
"All available evidence clearly points to Iran. There is no justification for this attack," said the statement, issued by current G7 chair, Britain.
The vessel was a Liberian-flagged, Japanese-owned petroleum product tanker managed by Israeli-owned Zodiac Maritime. As a result of the drone attack, two crew members - a Briton and a Romanian - were killed.
Tehran has denied any involvement.
In a separate statement, the US military said explosives experts from the Ronald Reagan aircraft carrier - which deployed to assist the Mercer Street - concluded the drone was produced in Iran.
It said the explosives experts were able to recover several pieces of a drone, including a part of the wing and internal components which it said were nearly identical to previously-collected samples of Iranian attack drones.
Britain, Israel, the United States and others have criticized Iran for the attack and vowed to respond.
"Iran's behavior, alongside its support to proxy forces and non-state armed actors, threatens international peace and security," the G7 statement said.
"We call on Iran to stop all activities inconsistent with relevant UN Security Council resolutions, and call on all parties to play a constructive role in fostering regional stability and peace."
Britain raised the issue at a closed-door meeting of the United Nations Security Council on Friday. No action is expected to be taken by the 15-member body.
"Iran was responsible for this attack. We know it was deliberate and targeted. There is no justification for what happened - a state sanctioned attack on a civilian vessel, passing peacefully through international waters," Britain's UN Ambassador Barbara Woodward told reporters after the meeting.
