"Europe must demonstrate its sovereignty and its power and that's the reason why the European Commission is going to propose countermeasures to President Trump's utterly untimely initiative," Le Drian told the CNews TV channel. "We have to give a firm response."
European commissioner Pierre Moscovici warned that the bloc has an "arsenal" of measures if Trump went ahead, threatening to target products from constituencies held by members of Trump's Republican Party, especially that of House of Representatives speaker Paul Ryan.
He named oranges, tobacco and bourbon as examples of the goods that would be hit.
"It is to make Congress understand that everybody loses," he told BFM TV, adding that Brussels may take the case to the World Trade Organisation.
The European Union has drawn up a list of US exports to be targeted if the tariffs come into effect.
Although European Commission chief Jean-Claude Juncker threatened reprisals against big-name brands like Levi's jeans and Harley-Davidson motorcycles, it does not name specific companies.
But it does mention "men's or boys' trousers and breeches of cotton denim" and "motorcycles including mopeds" with engines of 500cc capacity and above, as well as "some kinds of bourbon", steel, sweetcorn, cranberry juice and peanut butter.
Unveiling the list, European commissioner Cecilia Malmström warned that Trump's measures would threaten "thousands of European jobs".
The EU is also looking at "safeguard" measures to protect its own industry - restricting the bloc's imports of steel and aluminium to stop foreign supplies flooding the European market, which is allowed under World Trade Organisation rules.
Europe exports around five billion euros-worth of steel and a billion euros-worth of aluminium to the US each year.
The commission estimates Trump's tariffs could cost some 2.8 billion euros.