Iran's oil exports are becoming harder to track as Iranian tankers are increasingly "going dark" by turning off transponders that make them easy to detect as they transport their cargo on the high seas, oil experts say.
With the United States preparing to reimpose sanctions on Iran's oil and financial sectors on November 5, officials from Tehran to Brussels and Washington will be seeking information about whether the sanctions are working as intended to thwart Iran's sale and transport of oil around the world.
AFP reported on November 2 that in late October, every single tanker carrying Iranian oil suddenly "went dark," switching off their transponders to avoid being tracked, the first time that had been seen by the TankerTrackers monitoring group in Stockholm.
Even with the transponders switched off, firms that track shippers still can use satellite images to try to locate the vessels, but the loss of individual tracking mechanisms on board each ship will make that harder, the monitor said.
Oil and shipping analysts say that Iran used the same technique to hide its oil sales the last time it was subject to global sanctions from 2010 to 2015, switching off tracking systems in particular to hide the destinations of its oil shipments.
Before U.S. President Donald Trump's announcement in May that he would reimpose U.S. sanctions, Iranian crude exports peaked above 2.5 million barrels a day. Official statistics show they fell to about half that amount by the end of summer.
But analysts say the possibility that some shipments are not showing up in tracking systems means that estimates of Iran's oil trade have become more difficult and unreliable.
To illustrate, according to Refinitiv Eikon data, Iran exported 1.55 million barrels a day in the first three weeks of October. But Kpler, a data intelligence company, said the amount might have been as high as 2.2 million barrels.
Iranian officials have been cagey recently about how much oil they are selling and shipping, declining to give exact amounts while appearing to affirm estimates that exports have fallen significantly since April.
Iranian officials have insisted that it will keep exporting oil despite the U.S. sanctions, saying the United States will never achieve its target of reducing Iranian exports to "zero."
"Iranian oil exports cannot be stopped," Tasnim news agency quoted Oil Minister Bijan Zanganeh as saying on October 23.
Iranian Vice President Eshaq Jahangiri also recently said: "Despite sanctions, Iran's oil exports will not fall below a million barrels a day."
Iran's oil exports dropped below 1.2 million barrels under the previous global sanctions that were lifted under Iran's 2015 nuclear agreement in exchange for curbs on its nuclear activities.