OREANDA-NEWS. March 13, 2018. US president Donald Trump's proposal to impose stiff tariffs on imported steel and aluminum has presented an unexpected challenge to negotiations on the North American Free Trade Agreement (Nafta).

The seventh round of Nafta talks between Canada, Mexico and the US is scheduled to conclude today in Mexico City. Trump last week announced plans to impose a 25pc tariff on all steel imports and a 10pc tariff for aluminum — potentially affecting both Canada and Mexico.

US negotiators ahead of the current round of talks expressed confidence that the thorniest issues could eventually be overcome, to the relief of the US energy industry.

But Trump's unexpected proposal on tariffs and subsequent statements have cast a pall over the negotiations. Trump this morning via Twitter suggested Canada and Mexico would be exempted from the new measures only if "new and fair" Nafta agreement is signed.

"We have large trade deficits with Mexico and Canada. Nafta, which is under renegotiation right now, has been a bad deal for U.S.A. Massive relocation of companies & jobs."

Industrial groups in Mexico already have asked the government to retaliate with similar measures against US exports. Mexico should not be included in steel and aluminum tariffs, Mexican economy minister Ildefonso Guajardo said following Trump's tweet. "It is the wrong way to incentivize the creation of a new & modern Nafta," Guajardo replied, also via Twitter.

Canada likewise said it would consider retaliatory measures.

The exact details of the measures outlined by Trump are not clear. Trump's principal trade adviser Peter Navarro, an academic who opposes free trade and foreign investment, appears to have been behind the proposal.

Mexico and Canada were granted exemptions from steel tariffs imposed by the US in 2002 as it would have faced penalties under Nafta otherwise.

But Navarro in a televised interview yesterday said no country would be exempt from the tariff proposal. "As soon as (Trump) starts exempting countries, he has to raise the tariff on everybody else. As soon as he exempts one country, his phone starts ringing from heads of state of other countries."