By Bas van Geffen, senior macro strategist at Rabobank

This weekend’s events cast fresh doubts over the value of the US-Iran memorandum of understanding.

On Friday, President Trump condemned the drone attack on a container ship that was transiting the Strait of Hormuz. Trump posted on Truth Social that the US had shot down three other drones, adding that “obviously, this is a foolish violation of our Ceasefire Agreement.”

What followed was a series of eye-for-an-eye strikes. The US targeted Iranian military sites in retaliation for the attack on the container ship. And on Saturday, the US hit Iran again after the country attacked a tanker transporting Qatari oil.

Both sides have since agreed to halt their attacks and have said that further peace talks in Doha must go on. Or, that is what US officials believe, at least: “Our understanding is that both sides will stand down for now and vessels can move freely.”

That news seems to be sufficient to reassure financial markets today, with US equity futures indicating a moderately positive opening of the week. But will this new pinky swear to cease all aggression be enough to convince shipping companies, insurers, and ships that passage through the strait is once again safe?

Firstly, we would ask whether the US’ understanding is the same as Iran’s? Recall that both sides were already at odds over what “safe passage” meant in the first place, after Iran warned that only ships following the routes sanctioned by the IRGC are guaranteed safe transit. And “for now” does a lot of heavy lifting in that US statement too. Is that for the duration of the memorandum of understanding? Is it until the talks in Doha this week have concluded? Or just until either side decides otherwise?

Israel’s war against Hezbollah remains another potential trigger for renewed escalation in the strait. Hezbollah has rejected the framework agreement signed by Israel and Lebanon as a “surrender of sovereignty.”

Even if a number of ships is willing to sail through the Strait of Hormuz, the likely presence of sea mines limits the capacity of the strait. The CEO of NYK Lines told the FT that “the routes available for navigation are extremely limited,” adding that traffic will not return to normal “for months.”

The war between Russia and Ukraine may exacerbate global fuel shortages. Putin admitted that Ukrainian attacks on energy infrastructure are having effect. The Russian president acknowledged that businesses and motorists are facing fuel shortages, and he indicated that problems are likely to persist due to refinery outages: “the right type of gasoline isn’t always available right now.” The government is discussing measures, including a possible ban on diesel exports.

So, uncertainty about fuel supply remains high. Together with concerns about new US import tariffs, that’s driving shipping costs to new highs.

Last month, the US administration unveiled plans for new tariffs on a range of trading partners, after the Supreme Court annulled part of Trump’s original tariff scheme. So, US companies are trying to build inventory ahead of these tariffs. Just like the frontloading seen ahead of the “Liberation Day” tariffs, this stockpiling is putting pressure on shipping costs. According to data from Drewry, the freight rate for a 40-foot container has surged to the highest in about two years.

And so, new import tariffs –or the anticipation thereof– will probably continue to put upside pressure on US inflation, thereby delaying Fed Chair Warsh’ rate cutting campaign. In fact, some policymakers are considering a rate hike as their next move. Kashkari indicated which dot in the Fed’s dot plot is his: he said that he has pencilled in one rate hike in for this year, and that he expects rates to stay on hold in 2027. The central banker then added “we’re going to have to see how no forward guidance works.” Well, not like this?