Trump made the scathing remarks at the MAGA event in Southaven, where thousands of his core base turned out in support.
During the rally Trump launched a seething rant against Jean Claude-Juncker, citing the vast amounts of money the US has “lost” to the European Union as a result of trade tariffs.
He said: “The European Union, we lost $151billion – with a B! – to you.
“We lost $151billion. Jean-Claude, the head of the European Union, he is tough and smart, really tough – I don’t think he likes our country too much but I have told him that many times.”
Of the EU, Trump said: “They were formed in order to take advantage of us.”
The President continued: “Jean-Claude, for years the Obama administration wanted to negotiate and you said ‘no, we are not going to negotiate’.
“I’m telling you I want to negotiate – we lost 151billon dollars with the European Union.”
He added: “They are just killing us.”
Trump proceeded to mimic Mr Juncker’s voice and explain that after two weeks of attempting to talk to the EU, he still had no word from the President of the European Commission.
Acerbically impersonating the EU boss, he said: “I call him up again and say, Jean-Claude, we gotta’ negotiate and he says, ‘yes, yes’ – beautiful accent I wish I had his accent.
“I would have been President 15 years ago if I had his accent.
“I said, Jean-Claude, please! We have got to negotiate – $151billion we lose.
“You have barriers against our farmers – we can’t sell farm products.
“You have barriers against our cars – and yet you sell us millions of Mercedes and BMW, and all these cars they pour into our country.
“You have barriers and you charge us big tariffs for products.
“And you make it impossible for us to sell you products but you sell us so much.
“Jean-Claude, we have got to negotiate. Two weeks go by and I say Jean-Claude, you don’t have to negotiate anymore.
“I am going to put a 25 percent tariff on Mercedes Benz, BMW and every car you send into the United States.”
The President then proclaimed his administration would slap a 25 percent tariff on “millions and millions” of cars, to raucous applause from the onlooking crowd.
Trump claimed after he threatened the tariffs, Mr Juncker arrived in the US the next morning.
The firebrand Republican claimed he said to Mr Juncker: “Where did you come from, New York?”
But Trump disclosed the European Union boss had flown in from Europe.
Mocking the Brussels bureaucrat, he said: “Let me now the name of that plane – that is the fastest plane – and now they are dying to make a deal.”