John R. Bolton, President Trump’s national security adviser, on Wednesday accused Iran of playing a key role in recent attacks on ships off the coast of the United Arab Emirates, the latest instance in which he has articulated a more hawkish view than his boss toward Iran.

Ratcheting up his criticism of Tehran, Mr. Bolton tied the attacks this month on four oil vessels at the mouth of the Persian Gulf to “naval mines almost certainly from Iran,” apparently without presenting evidence.

President Trump withdrew last year from the 2015 nuclear accord that world powers struck with Iran and then reimposed broad sanctions, but in his comments to journalists during a visit to the emirates, reported by Reuters and The Associated Press, Mr. Bolton said there was “no reason” for Iran to breach the nuclear deal unless it were actually seeking atomic weapons.

“There’s no reason for them to do it unless it is to reduce the breakout time to nuclear weapons,” he told journalists in Abu Dhabi, according to The A.P.