"We are looking at the option to be excluded from those higher tariffs. We also will continue our preparatory work on potential re-balancing measures, hoping that we are not forced to use them," Katainen told a news conference in Brussels.
"... if the worst scenario happens, we are ready to take the U.S. to the WTO court. We are discussing with other allies, other partners to do it together," the EC vice-president said.
U.S. President Donald Trump signed proclamations on steel and aluminum tariffs amid global dissent on Thursday. With this move, the United States will impose a 25-percent tariff on steel imports and a 10-percent tariff on aluminum imports.
The tariffs will take effect in 15 days with initial exemptions for Canada and Mexico pending the renegotiation of the North American Free Trade Agreement (NAFTA).
The EU has said it has prepared a list of products including orange juice, bourbon, cranberries, peanut butter etc, on which it will impose reciprocal tariffs if needed.
"We expect that the whole EU is treated as a trading block which we are. All the countries are in a similar position. We cannot accept that the EU is divided into different categories," he added.
EC trade commissioner Cecilia Malmstrom, U.S. trade representative Robert Lighthizer, and their Japanese counterpart are scheduled to hold a trilateral meeting on Saturday in Brussels.