SIJ, which posted revenue of EUR 756m for 2017, exports about 9% of its production to the US. Statistics Office data show Slovenian steel and iron exports to the US totalling just under EUR 65m.

Impol exports about EUR 10m-worth of goods to the US annually, with total Slovenian aluminium exports at just under EUR 12m.

Neither company commented on the news on Thursday, but Economy Minister Zdravko Počivalšek said the tariffs could "jeopardise Slovenian economic growth."

The tariffs are "a stupid external issue that Slovenia cannot affect," he told the STA.

The EU was initially exempted from the US plan to introduce 25% tariffs on steel and 10% tariffs on aluminium products, but since the EU and US failed to reach a deal, the tariffs will enter into force on 1 June.

Even European companies not directly affected will feel the effects of the measure.

Analysts believe a more serious trade dispute could ensue, but there is also the risk that third-country producers unable to sell steel in the US will flood the EU market, driving down prices.