Mr Juncker was livid after the US decided to go ahead and impose hefty export tariffs on the bloc.
Voicing his fury hours after US President Donald Trump announced his protectionist move on Thursday, he said: “It makes me angry, worried and annoyed that we have been talking to the Americans for months.
“Mrs Malmström, the trade commissioner, has had 15 or 16 meetings with the US secretary of commerce.
“But they don’t listen. They think they can talk Europeans down and make them small.
“That is not going to happen. This is not the way to deal with allies — Americans and Europeans are allies after all.
“And when we are treated this way, we must react adequately, proportionally, sensibly and intelligently.”
Mr Juncker vowed the EU's reaction will come “within hours” and promised to take the dispute to the World Trade Organisation (WTO).
But Europe’s threat may not find application in reality for several weeks, as under WTO rules the EU needs to hold any retaliatory counter