Donald Trump described the European Union one of his greatest “foes” in an interview on American television on Sunday, just hours before sitting down to a high-stakes summit with Russian president Vladimir Putin.

Asked on 'CBS Evening News'  to name his “biggest foe globally right now”, the US president started by naming the European Union , calling the body “very difficult” before ticking off other traditional rivals like Russia and China.

Hours earlier, British prime minister Theresa May revealed that Trump suggested she “sue the EU” rather than go into negotiations over Brexit.

Trump, speaking in  Scotland, told CBS Evening News:  “Well I think we have a lot of foes. I think the European Union is a foe, what they do to us in trade. Now you wouldn’t think of the European Union but they’re a foe.”

Apparently taken aback, CBS anchor Jeff Glor replied: “A lot of people might be surprised to hear you list the EU as a foe before China and Russia.”

But Trump insisted: “EU is very difficult. I respect the leaders of those countries. But – in a trade sense, they’ve really taken advantage of us.”

Meanwhile, in an apparent reaction to Trump's claim about EU, Donald Tusk, president of the European council, tweeted:  “America and the EU are best friends. Whoever says we are foes is spreading fake news.”

Trump departed Scotland for Helsinki, where he is due to meet with Russian president, Vladimir Putin. However, many politicians in Washington , both Republican and Democrat ,  are concerned about how much common ground Trump will find with Putin when they meet at the Finnish presidential palace.