Tehran and Washington clashed over the Strait of Hormuz again this past weekend. Citing Israel’s latest attacks on Lebanon, Iran declared that it reclosed the strait. The U.S. was quick to contest that. Maritime tracking data showed that dozens of ships passed through on Saturday and Sunday, though far fewer than the daily average before the war.

President Donald Trump suggested the U.S. might impose its own tolls on strait crossings if a final deal with Iran was not reached during the countries’ 60-day negotiating period. Passage was free before the war, but Iran last month established a new governmental authority to collect money from ships and has said it still expects vessels to register with the Persian Gulf Strait Authority.

No one country owns the Strait of Hormuz, which borders both Iran and Oman. Last week’s memorandum of understanding allowed Iran to manage the strait for now while holding discussions with Oman and six other Gulf states “to define the future administration and maritime services” of the waterway. Iran agreed not to charge transiting vessels tolls for 60 days.

Legal experts and maritime associations have repeatedly stressed that a toll regime would upend decades of international trade precedent involving the world’s waters. If the U.S. and Iran cement a final deal, analysts say it could take months for the flow of oil, natural gas, fertilizer and other commodities to return to prewar levels.

Here’s a closer look at the status of the Strait of Hormuz:

Ships are moving but not at the prewar pace

Data and analytics company Kpler said its tracking confirmed 71 ships traveled through the strait between Friday and Sunday, with a peak of 35 crossings Saturday. In contrast, about 100 to 130 vessels a day made the journey before the U.S. and Israel launched strikes on Iran in late February, and Tehran responded with its own attacks and effective closure of the waterway.

As part of the provisional Iran-U.S. framework, Iran said it would conduct demining work within 30 days and remove “technical and military obstacles” to shipping. Iran’s lead negotiator and parliament speaker, Mohammad Bagher Qalibaf, told Iranian state media Monday that his country would manage the strait in accordance with international maritime law.

The main central route of the Strait of Hormuz is still mined and remains closed. Ships have been using the smaller northern route, which goes through Iranian waters, and the southern route, which goes through Omani waters. But “caution is still clear” in the many vessels either sticking to Iran’s prescribed route or trying to conceal their positions and identities by keeping their transponders off, Kpler said.

Both Iran and US have threatened tolls

Early in the war, Iran threatened to attack ships that tried to use the Strait of Hormuz without its approval and began vetting vessels in a pay-to-pass scheme that shipping analysts dubbed the “tollbooth.” Iran also demanded in early April the right to collect tolls as a precondition for relinquishing its chokehold on the strait.

Although the Trump administration imposed sanctions on the Persian Gulf Strait Authority late last month to oppose what Treasury Secretary Scott Bessent described as Tehran’s attempt to extort global maritime trade, the president on Saturday suggested the U.S. could impose its own tolls for “services rendered as the Guardian Angel to the countries of the Middle East.”

The administration has not provided details on how the U.S. would apply any charges on ships if talks with Iran do not yield a completed agreement. Shipping analysts have expressed surprise at how much control over the strait the inital agreement gave Iran.

“Almost all the power goes into Iran to determine the arrangements going forward in the future. This is what we really need clarity on,” said Philip Belcher, marine director of Intertanko, a trade group for independent tanker owners, said Thursday.

Experts say tolls would violate maritime law

Collecting tolls in the strait could violate an enduring principle of international maritime trade: freedom of peaceful navigation. The concept was codified by the United Nations’ Convention on the Law of the Sea, which took effect in 1994.

The treaty provides ships the right of unimpeded “transit passage” through more than 100 straits worldwide, including the Strait of Hormuz. It only applies to natural waterways, so authorities can charge fees for ships to traverse man-made waterways such as the Panama Canal and the Suez Canal.

Oman is among the more than 170 countries that have ratified the U.N. convention, but the U.S. and Iran are not. Maritime associations have argued that all nations remain subject to the treaty’s provisions.

James Kraska, a U.S. Naval War College professor of international maritime law, notes that the U.S. and Iran are both members of the International Maritime Organization, the U.N. agency that oversees safety and security measures in international shipping. Both countries also are parties to the International Convention for the Safety of Life at Sea, a treaty that governs standards for building and operating ships.

In straits like Hormuz, fees can only be applied at established ports of entry or for services specifically requested by a ship, such as specialized navigation aid through hazardous areas, according to Kraska, who is also a visiting professor at Harvard Law School..

“If Iran wants to apply those to everybody, then it has to adjust the traffic separation scheme rules, and that can only be done through the member states of the International Maritime Organization,” he said.

“You can’t impose fees for a ship exercising its right of transit passage,” Kraska added. “So the bottom line is, no — fees in this context are just not lawful.”

Countries sometimes have joined forces to share the costs of maintaining of a strait, he noted. For example, Indonesia, Malaysia, and Singapore worked with the International Maritime Organization and later other countries to develop such an agreement for the Strait of Malacca, but it involved negotiated contributions from the states using the passage, not fees on individual ships.

Disruptions could continue for months ahead

Conditions in the Strait of Hormuz have escalated or deteriorated quickly over the course of the war. While the outlook for shipping has improved since the U.S. and Iran pledged to extend their ceasefire, “there is a degree of nervousness around the situation,” said Marcus Baker, the global head of marine, cargo and logistics at insurance brokerage and risk management company Marsh.

“As far as the insurance position is concerned, there’s a good deal of support for ship owners that are trying to move out” during this period, but the interim deal between Iran and the U.S. does not include language for keeping the strait toll-free beyond the negotiating window, Baker said.

“We’ll see what the next six weeks brings us,” he said.