US President Donald Trump has hit back at Canada after Prime Minister Mark Carney announced retaliatory tariffs on American goods, escalating a trade dispute between two of the world's closest economic partners.

Canada's response follows the introduction of new 50 per cent US tariffs on roughly $20 billion worth of Canadian imports after last-minute negotiations between Washington and Ottawa failed to produce an agreement.

Carney said Canada would match the latest US measures "dollar for dollar", with retaliatory tariffs scheduled to take effect on September 8.

The Canadian measures are expected to target American steel, dairy products, electronics, appliances, agricultural equipment, pulp and paper, among other goods.

Trump responded on Sunday with renewed criticism of Canada, accusing the country of seeking favourable access to the United States while maintaining trade policies he considers unfair to American producers.

The latest confrontation comes after three days of intensive negotiations ended without a deal.

Washington and Ottawa have blamed each other for the collapse of the talks.

The United States maintains that Canada's trade policies discriminate against American producers in sectors including dairy, alcohol and automobiles.

Canada, however, says some of the final demands presented by the US government were economically unacceptable and would have restricted its ability to pursue independent trade policies.

The 50 per cent US tariffs took effect on Saturday after Trump had temporarily delayed their implementation for three days while negotiations continued.

Products affected include wine, furniture, clothing, dairy products, cement, fishing equipment and hockey products.

The measures cover around five per cent of Canada's annual exports to the United States.

Unlike some previous US tariffs, several products previously receiving preferential treatment under the United States-Mexico-Canada Agreement are also affected.

That development has raised wider questions about the future of the three-country trade pact.

The White House imposed the measures using Section 338 of the US Tariff Act of 1930, a rarely used provision allowing the president to impose tariffs of up to 50 per cent on imports from countries considered to discriminate against American commerce.

Carney said his government could not accept the latest US proposals and accused Washington of using the deep economic relationship between the two countries as leverage.

Canada sends a large majority of its goods exports to the United States, making the American market particularly important to Canadian businesses and workers.

Canadian officials have nevertheless signalled that Ottawa is prepared for a prolonged dispute and plans to introduce financial support for industries most exposed to the new US measures.

The Canadian government's planned retaliation is expected to affect US businesses as well.

Trade experts have warned that extended tariffs could raise costs for companies on both sides of the border, with some of those costs eventually reaching consumers through higher prices.

US Trade Representative Jamieson Greer has defended Washington's position and said the breakdown represented a missed opportunity for Canada.

He also indicated that the United States could introduce additional measures in response to Canadian retaliation.

No new round of formal trade negotiations has been announced.

The confrontation represents another deterioration in relations between two countries whose economies have been deeply connected for decades through cross-border manufacturing, energy, agriculture and consumer trade.

Canada's retaliatory tariffs are scheduled to begin on September 8, while additional details of the products affected are expected to be released before implementation.