BRUSSELS/WASHINGTON - U.S. Commerce Secretary Wilbur Ross will urge the European Union to lower its trade barriers, which are unfair to U.S. farmers and industry, Donald Trump said on Monday.

Firmly rejecting that view, the European Commission accused the U.S. president of "cherry-picking" data to twist what has become an increasingly fractious transatlantic debate.

The EU is seeking to be exempted from planned U.S. import duties of 25 percent on steel and 10 percent on aluminum, but says Washington has not made clear how the exemption process works.

Trump said in a tweet on Saturday the United States was ready to drop its tariffs if the EU lowered its "horrific" rates on U.S. products. On Monday, he tweeted that Ross would be speaking with EU representatives about eliminating "large tariffs and barriers"

"Not fair to our farmers and manufacturers," he said.

Representatives from the Department of Commerce did not immediately respond to queries on the content or timing of those discussions.

The Commission said it expected to be in contact with Washington over the metals tariffs this week, but that no formal talks had been scheduled. It was still hoping for a clearer indication about the exemption process.

It also said Trump was "cherry-picking" particular tariffs to highlight differences, and maintained average tariffs were very similar on each side of the Atlantic - 3 percent for products into Europe and 2.4 per cent for those entering the United States.

The U.S. tariff for cars, at 2.5 per cent, was lower than the EU rate of 10 per cent, but its rate of up to 25 per cent on trucks was higher. The Commission spokesman also pointed to U.S. import duties of up to 48 per cent on shoes, 12 per cent on textiles and 164 per cent on groundnuts.

"Cherry-picking particular tariffs in one category, like looking just at car tariffs on both sides, misses the whole picture, while not taking into account lower levels on other products does not give an accurate picture of tariffs in general," a Commission spokesman said.

"The EU market is one of the most open in the world and if anyone starts throwing stones, it's better first to make sure he is not living in a glasshouse."

The EU, he said, preferred dialogue, but was continuing its preparations for a "firm and proportionate" response.

The EU has been talking with partners about a legal challenge at the World Trade Organization to Trump's plan and is considering safeguards to prevent steel and aluminum, diverted from the United States, flooding into Europe.

It has also lined up 2.8 billion euros of U.S. products, from maize to motorbikes, on which to impose tariffs so as to "rebalance" trade flows.