Iran dismissed as "baseless" on Friday US accusations it executed twin attacks that left two tankers ablaze in the Gulf of Oman, raising fears of conflict in the strategically vital waterway.
China called for all sides to "resolve the conflict through dialogue" as oil prices jumped, while the European Union and the United Nations called for restraint.
Secretary of State Mike Pompeo warned Washington would defend its regional interests after US Central Command blamed Iranian forces for the attacks — the second in a month in the strategic shipping lane.
CENTCOM released grainy black-and-white video it said showed crew members of an Iranian patrol boat removing an "unexploded limpet mine" from the hull of Japanese-owned tanker Kokuka Courageous.
No proxy group could be responsible, Pompeo said. But Foreign Minister Mohammad Javad Zarif tweeted that the US had "immediately jumped to make allegations against Iran without a shred of factual or circumstantial evidence".