US President Trump’s 25% tariffs on products imported from Canada, China and Mexico have been met with a raft of retaliatory import taxes, amid fears that the measures may spark a wider trade war.

The three countries targeted by the tariffs are the US’s top trading partners – last year at least USD2.2 trillion in goods was traded between them.

The executive order widened the original 2018 tariffs for steel and aluminium under Section 232 of the Trade Expansion Act of 1962. The new tariffs end all exemptions, add more downstream steel and aluminium products, and create an exemption for steel “melted and poured” and aluminium “smelted and cast” in the US.

Specifically, all exemptions have been rescinded and, according to legal firm White & Case, which has analysed the orders, “existing exemptions on imports from Argentina, Australia, Brazil, Canada, the EU countries, Japan, Mexico, South Korea, Ukraine, and the United Kingdom” on steel no longer apply.

Likewise, aluminium imports from “Argentina, Australia, Brazil, Canada, the EU countries, Japan, Mexico, South Korea, and the United Kingdom” will also face the 25% tax.

Derivative products from steel and aluminium will also be covered by the new tariffs.

US Customs and Border Protection (CBP) will issue guidance on how importers should document supply chains of covered steel and aluminium derivative articles that were processed outside the US using inputs that were, respectively, “melted and poured” or “smelted and cast” in the US, according to the firm’s analysis.

Although the administration believes “the producers and the foreign countries as opposed to Americans” will bear the brunt of the tariffs, according to White House adviser Jason Miller, many economists are doubtful.

One US senator, Rand Paul of Kentucky, has tweeted: “US tariffs inevitably bring Canadian, Mexican, and Chinese tariffs which means higher prices for lumber, steel, aluminum and more expensive homes and cars.”

 Adding that retaliatory tariffs would also lead to less international shipping, he said: “Tariffs are taxes and if you tax trade you’ll get less trade and less prosperity.”

Indeed, Canada has responded with 25% tariffs on CAD155 billion (USD107bn) of goods. China faces 20% tariffs after Trump doubled it, but China’s exports to the US are less than 3% of national income, as following the first round of tariffs during his first presidency, China developed markets elsewhere.

Mexico will respond to the tariffs on Sunday 9 March.

US retailers have already said that the US consumer will be worse off. Chief executives at Target and Best Buy stores have said that prices are likely to rise “in the next few days”.