The president told German chancellor Angela Merkel last month that an EU-US trade deal would be “simpler that he thought”, The Times reported.
According to the newspaper, the conversation led to a “realisation” that a trade deal with the bloc would be more beneficial to America than one with Britain.
The Transatlantic Trade and Investment Partnership (TTIP) trade deal between the EU and US, which was shelved after Mr Trump's election victory, may now be revived or a new deal proposed, experts believe.
Last year, American exports to the bloc were worth $270 billion dollars compared to $55b worth of goods exported to the UK.
Imports to the EU made $147b compared to just $54b imported into Britain.