DUBAI/WASHINGTON — US President Donald Trump blamed Iran on Friday for attacks on two oil tankers at the entrance to the Gulf despite Tehran's denials.

Thursday's blasts followed similar attacks a month earlier on four tankers, which Washington also blamed on Tehran.

They come at a time of escalating confrontation between the United States and Iran. Last month Washington sharply tightened sanctions against Tehran, which in response has threatened to step up its nuclear activity.

Asked how he planned to address Tehran and prevent any further incidents, Trump told Fox News: "We're going to see." He also said that any move to close the Strait of Hormuz would not last long.

Nevertheless, Trump, who last year pulled the United States out of an agreement between world powers and Tehran to curb Iran's nuclear program in return for the lifting of sanctions, said that he was open to negotiations with Iran.

"We want to get them back to the table," Trump said. "I'm ready when they are." He added that he was in "no rush".

Iran has repeatedly said it will not re-enter talks with the United States unless it reverses Trump's decision to withdraw from the nuclear deal.

The US military released a video on Thursday it said showed Iran's Revolutionary Guards were behind the blasts that struck the Norwegian-owned Front Altair and the Japanese-owned Kokuka Courageous in the Gulf of Oman, at the mouth of the Gulf.

Iran said the video proved nothing and that it was being made into a scapegoat.

UN Secretary-General Antonio Guterres told the UN Security Council on Thursday the world could not afford "a major confrontation in the Gulf region".

The US military said black-and-white footage it filmed from a US aircraft showed Iran's Guards on one of their patrol boats drawing up to the Kokuka Courageous and removing an unexploded limpet mine from its hull.

Britain said it took the matter "extremely seriously" and, if Iran was involved, "it is a deeply unwise escalation".

The Japanese-owned tanker, abandoned by its crew, was being towed to a port in the United Arab Emirates on Friday, after a Dutch firm said it had been appointed to salvage the ships.

The second tanker, the Front Altair, which was set ablaze by a blast, was still languishing at sea, although the fire that had charred the hull had been put out. — Reuters