FILE - White House national security adviser John Bolton talks to reporters about Venezuela,  in Washington, May 1, 2019.
FILE - White House national security adviser John Bolton talks to reporters about Venezuela, in Washington, May 1, 2019.

U.S. National Security Adviser John Bolton said Wednesday that Iran was "almost certainly" responsible for attacks earlier this month on oil tankers off the coast of the United Arab Emirates.

Speaking to reporters during a visit to the Abu Dhabi for what he called talks on "important and timely regional security matters," Bolton did not give any evidence to back up his accusation, but said the tankers were hit by naval mines.

Iran previously denied responsibility for the attacks, and on Wednesday foreign ministry spokesman Abbas Mousavi rejected Bolton's accusation as “ridiculous,” but not a surprise since Bolton is a long-time critic of Iran.

Tensions between Iran and the United States have escalated in recent weeks since President Donald Trump announced his decision to try to totally eliminate Iran's oil exports to pressure the Iranian government to alter its aggression in the Middle East, and his move to add 1,500 troops in the Persian Gulf region in response to what he said were Iranian threats.

Iran's Foreign Minister Mohammad Javad Zarif has accused Bolton and others of engaging in "warmongering" and said the Trump administration with its re-imposition of sanctions against Iran is conducting "economic terrorism."

Even so, Iranian President Hassan Rouhani told a Cabinet meeting that the “road is not closed” to negotiations with the U.S. if it returns to the 2015 international nuclear deal that Trump abrogated. The pact was aimed at curbing Tehran’s nuclear weapons development while lifting economic sanctions on Tehran.

“The road is not closed for them, whenever they put aside their cruel sanctions and return to the negotiation table they they left,” Rouhani said.