At least three tankers carrying Russian diesel to the United States have changed course, casting doubt over US President Donald Trump’s October deal with his Russian counterpart, Vladimir Putin.

Nearly a month after Trump agreed to let Russia release diesel stocks to the US and global markets, despite existing sanctions, zero diesel has reached the US, where prices have nearly doubled since the start of the US-Israel war on Iran.

Russia has sent out a total of four tankers loaded with diesel since the deal was agreed.

Here’s what we know.

What’s happened to tankers carrying Russian diesel to the US?

The Russian tanker Talisman and the Sierra Leone-flagged Leruo left the Baltic port of Primorsk last month, with the US East Coast as their declared destination.

As of Thursday, however, one was heading towards Brazil and the other into the Mediterranean, according to marine analytics firm Kpler and the vessel-tracking site MarineTraffic.

A third tanker, still in the North Atlantic, has changed its destination from New York “for orders”, leaving its unloading point open.

The Financial Times also reported that Beast, a sanctioned Seychelles-owned tanker that was loaded at the Russian port of Primorsk in late October, has set sail towards the US and is currently signalling “Atlantic”.

What did Trump and Putin agree?

A deal big on numbers, but scant on details.

Trump first announced the agreement following a call with Putin on October 9. He said Russia would make more than 300,000 tonnes of diesel available immediately to US and global markets.

Long-range product tankers, which carry diesel supplies, can carry up to about 100,000 tonnes of diesel at a time.

Another 500,000 tonnes would follow in November, then 1 million tonnes “immediately thereafter”, Trump wrote on his Truth Social platform.

The agreement Trump brokered with Putin allows Russian diesel to be sold, delivered, unloaded and imported until April 7. It came after Trump blamed Ukraine for causing diesel shortages by targeting Russian energy facilities amid the Russia-Ukraine war.

It also reversed years of US policy after Washington banned imports of Russian energy following Moscow’s full-scale invasion of Ukraine in February 2022.

The Office of Foreign Assets Control (OFAC) of the US Department of the Treasury has since issued a temporary sanctions exemption, much to the ire of a cross-party group of lawmakers in the US Congress who passed a new sanctions package in the name of the late, pro-Ukraine Senator Lindsey Graham in September.

In a statement to the AP news agency, the Treasury said the exemption was “in compliance with all applicable laws”.

Russia announced its first shipment of diesel during a visit to St Petersburg in October by US Special Envoy Steve Witkoff.

Yet much about the deal remains unclear.

Neither the White House nor the Kremlin has said whether the agreement was put in writing, and neither has revealed the price to be paid for the diesel, the payment terms or which companies are involved.

How much Russian diesel is now waiting to be sold?

It’s not clear exactly, but it’s less than was promised.

The volumes involved have not been made public, but analysts say the first shipment is unlikely to deliver meaningful relief to US consumers.

US retail diesel prices topped $6 a gallon ($1.59 per litre) in September – nearly twice their pre-war levels – and have remained elevated.

“The reported shipment is equivalent to roughly two hours of US distillate consumption,” Aarathi Krishnan, CEO of Raksha Intelligence, told Al Jazeera, referring to the first tanker to be dispatched by Russia.

“Even if it arrives as planned, it will make very little difference to national supply,” he said.

Why don’t traders want to buy Russian diesel?

Because of the legal risk.

Despite the US Treasury temporarily authorising Russian diesel sales that would normally fall under sanctions, Congress’s ban on Russian energy imports remains in place, leaving a high level of uncertainty for traders.

New Jersey Governor Mikie Sherrill wrote to port and terminal operators in her state on Monday, telling them to turn away ships carrying the fuel.

She warned that “any effort to profit from the illegal trade in Russian fuel will be met with harsh penalties.”

Sherrill argued the Trump administration had no authority to override the ban.

Lawmakers have also warned banks, port authorities and fuel distributors that handling the imports could expose them to civil or criminal liability, as well as future congressional investigations.

The Trump administration claims the exemption is lawful, and no court has ruled on the dispute.

“It’s clear there’s hesitancy here in bringing these barrels onshore just because of the implications of doing so,” Matt Smith, an analyst at Kpler, told AP.

Where will the diesel go now?

Probably not to the US, experts say.

The first two diverted tankers are heading towards Brazil and the Mediterranean, according to Kpler data, and the third tanker could follow.

“Because of regulatory [and] sanctions concerns, we may not see this cargo discharge on the US Atlantic coast,” Smith told AP.

Moscow, however, insists the deal is on track.

Kremlin spokesman Dmitry Peskov said “all the diesel will find its buyers.”

Putin’s special envoy, Kirill Dmitriev, went further, writing on X that the reports were “fake” and “tankers destined for the US continue on course.”