As Donald Trump's proposed trade tariffs on steel and aluminium continue to cause concerns around world markets, Export New Zealand doubts there'll be an immediate impact on this country because most steel made here is used in the domestic market.

Executive director Catherine Beard says what's more worrying is the general idea of protectionism.

"It's really the opposite of the way that we want the world to go in terms of free and open trade, New Zealand depends on that a lot."

Beard says the Trump tariffs could potentially start a trade war with China, and other countries.

The US President says putting a 25 percent tariff on steel from other countries will help protect American jobs.

But the prospect of other countries retaliating if Donald Trump slaps tariffs on imported steel and aluminium seems to be growing.

The EU President has already talked about putting taxes on Harley Davidsons and Levi's jeans.

And Canada's Prime Minister Justin Trudeau says the idea of tariffs is absolutely unacceptable and would have significant and serious ramifications.

"That's why we are impressing upon the American administration the unacceptable nature of these proposals which are going to hurt them just as much as they are going to hurt us."

Mexico's Trade Minister Herminio Blanco Mendoza says a tax on steel would disrupt an integrated market.

"Anything that will distort that integration will not be good news for North America and definitely will make our industries less efficient in terms of competition."