President Donald Trump has doubled down on pressure against trade partners, threatening to tax European autos after the EU proposed stiffer tariffs on Harley-Davidson, bourbon and American blue jeans.

'If the E.U. wants to further increase their already massive tariffs and barriers on U.S. companies doing business there, we will simply apply a Tax on their Cars which freely pour into the U.S.' Trump tweeted on Saturday afternoon.

'They make it impossible for our cars (and more) to sell there. Big trade imbalance!' he continued.

Last year, the US ran a $151billion trade deficit with the EU, accounting for about one-fifth of America's $796billion global trade deficit.

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President Donald Trump has doubled down on trade pressure, prompting threats of retaliation from European leaders like German Chancellor Angela Merkel (right)

'The United States has an $800 Billion Dollar Yearly Trade Deficit because of our "very stupid" trade deals and policies,' Trump said in another tweet on Saturday. 'Our jobs and wealth are being given to other countries that have taken advantage of us for years. They laugh at what fools our leaders have been. No more!'

On Friday, angered by Trump's plan for tariffs on steel and aluminum imports, the EU announced plans to further penalize certain American exports to the bloc.

'We will put tariffs on Harley-Davidson, on bourbon and on blue jeans - Levis,' European Commission President Jean-Claude Juncker told German television. 'We are here and they will get to know us.'

A spokesman for German Chancellor Angela Merkel, the de facto economic leader of the EU, said US steel tariffs would hurt international commerce.

'The German government will look very closely at this decision and then assess the impact on the German and European economies,' said spokesman Steffen Seibert.

Trump said on Thursday the United States would apply duties of 25 percent on imported steel and 10 percent on aluminium to protect domestic producers.

'We will put tariffs on Harley-Davidson, on bourbon and on blue jeans - Levis,' said European Commission President Jean-Claude Juncker (pictured)

Data from European steel association Eurofer shows the United States was the destination of about 15 percent of Europe's steel exports in 2017.

Canada also has said it will retaliate for any US tariffs on steel and aluminum.

Australia's trade minister has spoken with his US counterpart to seek an exemption to Trump administration tariffs on steel and aluminium exports.

'Unfortunately, at this stage, it is not clear to me or to Australia whether or not we will be captured by the president's announcement,' Steve Ciobo told Sky News on Sunday, after speaking with US commerce secretary Wilbur Ross on Saturday.

Trump officially has until April 11 to announce his final decision on a steel tariff.

An analyst at Jefferies said they expected the final policy to be more nuanced than a blanket tariff, due to a mounting pushback from domestic steel consumers and foreign steel suppliers.