The EU's energy commissioner has urged Donald Trump to maintain a "free flow" of diesel following the US president's threat to cut off supplies, warning Europe already faces its "worst winter" for energy prices since 2022.

Dan Jørgensen told the Financial Times that it was in both the US and Europe's interests to "have as free a flow of energy between our countries as possible". But even with uninterrupted US diesel supplies, "this winter might be very, very bad [for Europe] and it might be the worst one we've had since 2022", he said.

European diesel prices are close to record highs. Trump rattled the market earlier this week when he said he would back a ban on diesel exports — a move traders warned would be "catastrophic" for Europe as the US is its biggest supplier. Although US energy secretary Chris Wright later cast doubt on the merits of a full embargo, the threat is the latest challenge to Europe's energy security as the conflict in the Middle East continues to disrupt global energy supplies.

Jørgensen said the European Commission was assessing short-term measures to lower the price of fossil fuels in the EU after French President Emmanuel Macron earlier this week called for immediate action, including the postponement of stricter conditions on methane imports and a softening of rules on fuel refining.