The European Commission said it was concerned by media reports this week that the US president could prevent diesel from reaching the global market, warning that an export ban would "negatively affect both sides."
Reports have suggested the measure under consideration would last 90 days and come ahead of US midterm elections. EU officials said the potential disruption to supplies could push diesel and other fuel prices higher across Europe.
The Commission did not lay out specific countermeasures but framed its reaction in terms of the wider economic consequences for the transatlantic relationship, signalling anxiety in Brussels about abrupt restrictions on energy trade.
Analysts have warned that any sudden reduction in available diesel on global markets can reverberate through refined-fuel prices, transport costs and industrial supply chains, especially in regions that rely on imports to meet demand.
The development adds to a series of trade and geopolitical tensions between the EU and the United States in recent years, and officials in both capitals will be watching for confirmation or clarification of Washington's intentions as the story develops.