The port operator of the two vessels, Bavand and Termeh, reported to Reuters that both vessels arrived in Brazil two months ago, carrying urea, a petrochemical product used as fertilizer. Although they were expected to load corn and continue their journey back to Iran, they weren't able to sail because of lack of fuel.
Also, the two vessels were amongst several ships that belong to the Iranian state company Sapid Shipping Co that have brought urea to Brazil this year and returned with corn. Urea is included in the US sanctions, but a local company decided to take that business.
For the time being, food is not covered by US sanctions and Iran is one of the top buyers of Brazilian agricultural commodities. Yet, Reuters states that trade is not usually conducted by Iranian-flagged vessels, and in the possibility that the vessels are Iranian, they have enough fuel to return without refuelling.
In the meantime, Petrobras confirmed that it declined to fuel the vessels and cited the sanctions.
According to Petrobras, the vessels were listed in the Specially Designated Nationals and Blocked Persons List, so that selling fuel would lead to penalties, since it operates in the US and shares listed in New York.
A Reuters' source added that the Iranian vessels' company took the case in Paraná courts, to force Petrobras fuel the vessels, with no success.
The last solution, under the possibility that the vessels are unable to find another company to fuel, is that Iran should send a vessel with fuel supply to Brazil.