The US blamed Iran for the attacks on Thursday, a charge Tehran rejected. Amid the rising tensions, Guterres said he was available to mediate if the parties agreed, however he added that "at the present moment we don't see a mechanism of dialogue possible to be in place."

The US and Iran have both said they have no interest in starting a war, but this has done little to assuage concerns that the two arch foes could stumble into a conflict. Guterres said the world cannot afford a major confrontation in the Gulf.

"It's very important to know the truth and it's very important that responsibilities are clarified. Obviously that can only be done if there is an independent entity that verifies those facts," he told reporters, adding that he believed only the Security Council could order a UN investigation.

UN political affairs chief Rosemary DiCarlo met with Iranian Foreign Minister Mohammad Javad Zarif on Friday on the sidelines of a Shanghai Cooperation Council meeting in Kyrgyzstan, UN spokesman Stephane Dujarric said.

He added that Guterres and his staff had been in contact with many of the countries concerned to tell them of the need to avoid any escalation.

Guterres, who condemned the attacks on the tankers, was speaking on Friday alongside Arab League Secretary-General Ahmed Aboul Gheit after the pair met.

Gheit told reporters that he did not believe an Arab country was "trying to obstruct naval lanes or to shoot itself in the foot by acting the way we have seen in the Gulf of Oman or in the Hormuz Strait."

"My call to our Iranian brothers - be careful and reverse course because you're pushing everybody towards a confrontation that no-one would be safe if it happens," he told reporters.

Australian Associated Press