They have to be stopped somehow from just pushing on with actions which they know are against the rules

Asian diplomat

The nations, in Geneva for talks at the World Trade Organisation (WTO) with US officials, warned of heightened action to fight the duties.

The EU will be entitled to request a WTO probe into the tariffs from 6 May, two months after it lodged its initial complaint.

'Systematic abuse'

But while Washington has on six previous occasions been found guilty by the WTO of imposing illegal trade safeguards, the 20 protesting nations expressed disappointment the findings had failed to stop US protectionism.

The US had committed "systematic abuse" of WTO laws, said a statement from the 20 nations.

"They have to be stopped somehow from just pushing on with actions which they know, whatever they say in public, are against the rules," one Asian diplomat said.

Washington has defended the tariffs, of up to 30%, as necessary to defend its ailing steel industry from foreign rivals which have received significant state support.

Lengthy process

The WTO has previously condemned US blocks on trade in goods from wheat to underwear.

But officials have expressed dismay over the length of time WTO investigations take.

The WTO can take up to a year to make a ruling, with appeals then permitted.

Officials from the EU, where steel producers stand to lose $2.4bn a year to the tariffs, fear the US will attempt to drag out the procedure for a long as possible.

While the EU is mulling retaliatory action, the US has said that the introduction of further duties without waiting for a WTO ruling would undermine the organisation's credibility.

The other three protesting nations represented in Geneva were Norway, Switzerland and South Korea.

Five of the countries represented - Britain, France, Italy, Japan, Germany - are, along with the US, members of the important G7 group of leading industrialised nations.