The European Union is ready to react swiftly if the United States restricts its exports, the European Commission said after US President Donald Trump threatened to confront the bloc over its "very unfair" trade policy.

Trump said in an interview with Britain's ITV broadcast on Sunday that he had a lot of problems with the EU and that it could "morph into something big" on trade.

A commission spokesman told a news conference that the European Union did not view trade as a zero-sum game.

"It is not about winners and losers. We here in the European Union believe that trade can be and should be win-win," spokesman Margaritis Schinas said.

"We also believe that while trade has to be open and fair it has also to be rules-based. The European Union stands ready to react swiftly and appropriately in case our exports are affected by any restrictive trade measures from the United States," he said.

Washington last week imposed tariffs of 20 percent on imported washing machines and of 30 percent on incoming solar cells and modules, among the first unilateral trade restrictions made by the administration as part of a broader protectionist agenda.

China and South Korea condemned the tariffs, with Seoul set to complain to the World Trade Organization (WTO).

The European Commission said then that it regretted the U.S. move, had serious doubts that it met WTO conditions and would analyse the impact on EU exports.