Seven oil tankers carrying an estimated 288,000 tonnes of Russian diesel are now sailing toward the United States, Greenpeace said, though it is uncertain whether the vessels will be able to unload amid a dispute over the legality of the shipments. The transport is the first phase of a supply deal negotiated between Presidents Donald Trump and Vladimir Putin earlier this month that has drawn opposition, reversing years of sanctions on Russian oil.

Previous reports had counted three tankers that departed Russian oil terminals in the Baltic Sea. Using shipping tracking websites and a range of other sources, Greenpeace said it believes its monitoring exercise is the most complete yet.

One of the seven tankers, Taurus, is relatively close to the US, Greenpeace said. When the map was first published, five of the others were close to the UK, and three were sailing through or into the English Channel. Among the vessels Greenpeace is tracking is the PVT Azura, said to be carrying Russian diesel to the US.

Shaun Burnie, an energy specialist with Greenpeace Ukraine, argued that with the location of the tankers plotted on a map, the shipments should be halted by Congress or local authorities in the US. “Instead of rewarding Russia for its vile war against Ukraine, there needs to be more punitive sanctions against Russia,” he said. “These shipments can be stopped.”

Putin agreed to supply the US with 1.8m tonnes of diesel in a surprise deal announced on 9 October, starting with 300,000 tonnes immediately. Trump announced a six-month waiver on existing sanctions to allow the shipments to proceed. Russia had been hit by waves of economic sanctions from the US, EU, UK and other leading western economies since Putin launched the full-scale invasion of Ukraine in February 2022, but this autumn Trump altered course and tried to work more closely with Putin even though Russia has not stopped attacking its neighbour.

Earlier this week, a group of US lawmakers led by a handful of Democratic senators warned banks and port authorities that they could face congressional investigations and other legal action if they handled the Russian diesel.

Mikie Sherrill, the Democratic governor of New Jersey, said she was looking at how to prevent the diesel from being unloaded if an attempt was made to do so in her state. She described the deal as “corrupt and illegal”.

There have been reports that the White House has been trying to encourage US firms to take the oil, though it is not clear buyers are forthcoming given the legal risks so close to next Tuesday’s midterm elections. Trump’s popularity has waned as fuel prices in the US have soared since he attacked Iran in the spring. Polling suggests a high likelihood that control of the House of Representatives could pass to the Democrats in the elections, while the battle over the Senate is considered too close to call.

Trump has argued that the Russia deal would help lower diesel prices, though the price per gallon has risen from $6.28 at the time the agreement was announced to $6.33, according to the American Automobile Association.

Ukraine’s president, Volodymyr Zelenskyy, denounced the agreement because the money raised would help the Kremlin fund the ongoing war. “Backroom deals” gave Putin more chances on the battlefield, he said.

The Kremlin has been trying to keep information about the latest oil exports secret. A presidential decree from the end of September restricted the publication of information about oil exports in an effort to evade international sanctions.

The developments came as 14 people were reported killed on Thursday morning when a Russian drone struck a crowded train platform in the central city of Dnipro, with five others reported killed in daytime strikes in Chernihiv and Kremenchuk. Ukrzaliznytsia, Ukraine’s state railway company, said a high-speed jet-powered drone had struck as a commuter train was preparing to depart Dnipro’s main station. Bodies lay scattered after the relatively unusual daytime attack, which took place at around 11am.