US Secretary of State Marco Rubio on Thursday warned that any tolls on ships passing through the Strait of Hormuz would set a precedent and risk “total chaos,” while Oman said no fees would be imposed.

Rubio’s comments during a tour of the Gulf came hours after Iran repeated that ships must seek its authorisation before crossing.

The statement by Iran’s Revolutionary Guards followed an announcement by neighbouring Oman of a new temporary shipping route through the strait running close to its coast, which Iran appeared to denounce.

Oman’s top diplomat, for his part, said no transit fees would be imposed in the Strait.

Badr Albusaidi said “future arrangements regarding the Strait do not entail the imposition of any transit fees,” during a meeting of Gulf foreign ministers in the Bahraini capital Manama with US Secretary Marco Rubio, whose administration has repeatedly opposed any fees or tolls.

Iran’s foreign minister, Abbas Araghchi, later “emphasised the importance of continued coordination” with Oman.

“International waterways do not belong to any nation-state. This is a foundational principle in the world today, without which the world would be in total chaos,” Rubio told a Gulf Cooperation Council meeting in Bahrain.

“If in fact, we accepted that you can charge money to use an international waterway because it happens to be near your territorial space, well then, this will spread throughout the world like a contagion.”

The future of the strait, a vital route for energy shipments that was blockaded by Iran during the war, is a key sticking point in negotiations between Tehran and Washington to end their war.

Tehran has said it plans to impose what it calls maritime service fees, as opposed to tolls, while the United States argues it is an international waterway and therefore should not be charged.

“The only authorised route for passage through the Strait of Hormuz is the route announced by the Islamic Republic of Iran,” said the Revolutionary Guards, the ideological arm of Iran’s military.

Any crossing without authorisation is “unacceptable and extremely dangerous”, they said in a statement, warning that vessels not complying “will be dealt with”.

They also appeared to denounce the new route released by Oman, but only referred to “certain authorities” rather than Muscat directly.

Oman, which sits on the other side of the strait from Iran, said the new corridor was coordinated with the International Maritime Organisation, a UN agency responsible for marine safety.

The only route currently authorised by Iran runs through a corridor that follows the Iranian coast.

Hormuz is a narrow stretch of water between Iran and the Gulf countries through which roughly 20 percent of the world’s crude oil and liquified natural gas normally transits.

At its narrowest it is only about 30 kilometres (18 miles) wide.

A memorandum of understanding signed last week by Tehran and Washington to end their war stipulated that commercial ships may transit the strait free of charge for the next 60 days.

With Iran and the US in further negotiations, it is unclear what arrangements will be in place after that period.

Rubio said the US wants a lasting settlement with Iran to end their war but not “at any price”.