Trade tensions between the European Union and the United States ran high yesterday as the clock was ticking for US steel and aluminium tariffs against European producers to kick in, reports AFP from Paris.

US Commerce Secretary Wilbur Ross on Wednesday rejected calls to extend exemptions on the punishing import tariffs and warned that duties for massive US imports of automobiles were on the horizon.

The prospect of the metals tariffs taking effect on Friday caused mounting frustration in Europe, the single-largest source of US steel imports.

"World trade is not a gunfight at the O.K. Corral," French Economy Minister Bruno Le Maire quipped Thursday, in reference to a 1957 western movie.

Le Maire warned that the EU would take "all necessary measures" if the US imposed the tariffs.

"It's not everyone attacking the other and we see who remains standing at the end," he said, declaring that the stiff taxes would be "unjustified, unjustifiable and dangerous".

German Chancellor Angela Merkel said the EU would respond in a "firm and united" manner to the tariffs.

"We want to be exempt from these tariffs" which were "not compatible" with World Trade Organization rules, Merkel told a press conference with Portuguese premier Antonio Costa in Lisbon.

German Foreign Minister Heiko Maas meanwhile warned against the threat of protectionism, telling reporters Thursday that international partners could have "no interest in the clock being turned back" on trade policy.

"To put it clearly: protectionism and isolation with regard to free trade must be kept from getting the upper hand again," he said after talks with his Chinese counterpart Wang Yi.

The Wall Street Journal reported on Wednesday that Washington would allow the EU exemption to expire, after weeks of talks failed to yield a compromise, such as a quota arrangement.

EU-US tensions are casting a shadow over a meeting of finance ministers from the world's top economies which opens in a Canadian mountain resort on Thursday.

The harsh duties imposed in March to combat global overcapacity of the metals and boost domestic production, were only among a flurry of different developments, coinciding with a political crisis in Italy, which this week has roiled markets.

US Treasury Secretary Steven Mnuchin is due to hold meetings with his European counterparts to discuss President Donald Trump's confrontational trade agenda, officials said.

But Jacob Kirkegaard, senior fellow at the Peterson Institute for International Economics, told AFP that the agenda Canada, the current G7 chair, set for the meeting -- which included uncontroversial themes such as inclusive

development and innovation in finance -- would be swept aside amid raw relations between America and its traditional allies.

"Hopefully they can agree to keep talking about these issues, although that is unlikely," he said, adding that Trump's recent actions proved to US allies that Washington would not de-escalate the dispute.