US Secretary of State Mike Pompeo said on Thursday that the United States has assessed, based on intelligence, type of weapons used and level of expertise needed, that Iran is responsible for the attacks on tankers in the Gulf of Oman.
He offered no concrete evidence to back up the assertion.
"It is the assessment of the United States government that Iran is responsible for the attacks that occurred in the Gulf ofOman today," Pompeo told reporters.
"This assessment is based on intelligence, the weapons used, the level of expertise needed to execute the operation, recent similar Iranian attacks on shipping, and the fact that no proxy group operating in the area has the resources and proficiency to act with such a high degree of sophistication," Pompeo said.
Two oil tankers were attacked on Thursday and left adrift in the Gulf of Oman. The attack drove up oil prices and stoked fears of a new confrontation between Iran and the United States.
The White House said President Donald Trump had been briefed.
Washington accused Tehran of being behind a similar attack on May 12 on four tankers in the same area, a vital shipping route through which much of the world's oil passes.