Shippers in Asia and Europe said confidence in resuming transit through the Strait of Hormuz could take weeks to rebuild and navigation will only restart once safety is assured, after the US and Iran agreed a framework deal to reopen the waterway.
US and Iranian officials are expected to sign a memorandum of understanding to end their war and reopen the strait on Friday. Global oil prices fell about five per cent on Monday in response.
President Donald Trump said in a social media post that ships loaded with oil are starting to move out of the strait, "going along the Southern 'Highway,' which is totally safe, secure, and pristine".
There were no significant tanker crossings visible in vessel-tracking data on Monday, aside from one LNG carrier, however ships have been quietly moving barrels along Oman's coast for weeks, sailing "dark" with US Navy support.
The data, which captures only vessels actively transmitting their positions, showed dozens of tankers clustered on both sides of the Strait of Hormuz.
Shippers welcomed news of the deal, but are waiting for more details, including on clearing mines.
"AIS data shows no wave of ships heading towards Hormuz this morning," Jyske Bank analyst Haider Anjum said in a client note.
"The shipping companies probably want to wait until it is clear that the agreement holds, as we have already had Hormuz 'open' for a very short time twice before," he added.
The Iran war that began on February 28 with US-Israeli strikes has largely stopped shipping through the transit route for around a fifth of the world's oil and liquefied natural gas supply, along with products such as aluminium and urea.
While traffic remains limited, India's Petronet sent the LNG tanker Disha through the strait on Monday, the only visible shipment so far, data from Kpler and LSEG showed.
The tanker, which loaded at Qatar's Ras Laffan on March 1-2 and had been west of the strait since, was expected to arrive at India's Dahej terminal on June 18, an Indian federal shipping ministry official said.
Shipping association BIMCO said it still considers transit through the strait highly risky, with mines a key concern.
"The next step is for shipowners to be reassured that transiting the Strait of Hormuz is not only permitted, but also safe," BIMCO's chief safety and security officer Jakob Larsen said on Monday.
"The news of an agreement is clearly positive," said Stefano Messina, head of Italian shipowners' association Assarmatori.
"However, in recent months there have been several announcements of a halt to the conflict, or at least of a truce, and unfortunately they have never been followed by concrete action," he added. A spokesperson for the Japanese Shipowners' Association said that while it welcomed the peace agreement, it wanted to, "wait a little longer for more concrete information".
"Given the situation, we cannot simply say, 'Right then, let's go' based on news of the agreement alone," he added.
Nippon Yusen, Japan's biggest shipper, said it hoped operations would return to normal as soon as possible, while Mitsui OSK Lines said it would only resume navigation once safety has been fully confirmed.
German shipowners' association VDR said it was "cautiously optimistic" about whether the deal could reopen the strait, while shipper Hapag-Lloyd said it hoped that vessels will be able to cross it this week.
The Norwegian Shipowners' Association said details of the agreement and the framework for any transit remain unclear, as does the extent of mines laid in key shipping lanes.
Norway-headquartered shipping group Wallenius Wilhelmsen said it was, "too early to comment on operational implications", while Oslo-listed Frontline, one of the world's largest tanker companies, said it viewed the development positively.
Danish shipping giant Maersk welcomed the deal, but also said it was too early to assess its impact and that it was making no changes yet to its Middle East operations.
An estimated 155 tankers, carrying oil and chemicals, were in the gulf area as of June 15, ship-tracking data from Kpler showed, down from 201 at the end of May.
Oil Brokerage's estimate stood at 215 tankers. Under unrestricted navigation, the traffic pile-up on either side can be resolved in eight to 10 days, said Anoop Singh, its global head of shipping research.
It would require weeks of de-mining and normalisation of insurance rates for resumption of meaningful traffic, said David Jorbenaze, global oil market leader at ICIS.
"Returning to full pre-conflict volumes is realistically a 2027 story, and only if the agreement holds without incident and production recovers at pace," he added.
(Reporting by Emily Chow, Jeslyn Lerh and Trixie Yap in Singapore, Nidhi Verma in New Delhi, Kentaro Okasaka and Maki Shiraki in Tokyo, Stine Jacobsen in Copenhagen; Additional reporting by Ludwig Berger in Frankfurt, Marie Mannes in Stockholm, Anushree Mukherjee in Bangalore, Elvira Luoma in Gdansk and Elisa Anzolin in Milan; Writing by Florence Tan and Nerijus Adomaitis; Editing by Tom Hogue, Jan Harvey and Alexander Smith)