US Secretary of State Mike Pompeo pinned attacks on two tankers in the Gulf of Oman on Iran Thursday, just hours after the Pentagon deployed a nearby destroyer to assist victims of the blast.

In brief remarks at the State Department, the top US diplomat insisted that only Tehran was capable of launching the attacks that incapacitated Norwegian and Japanese shipping vessels.

“It is the assessment of the United States government that the Islamic Republic of Iran is responsible for the attacks in the Gulf of Oman today,” Pompeo said. “These attacks are a threat to international peace and security, a blatant assault on the freedom of navigation and an unacceptable escalation of tension by Iran.”

Pompeo, who presented no hard evidence and left the podium without taking questions from the press, said Tehran was acting out on an April promise to shut down the Strait of Hormuz in an effort to see “our successful maximum pressure campaign lifted.” Pompeo said acting US envoy to the United Nations Jonathan Cohen would raise the attacks in a Security Council meeting Thursday.