WEST MIFFLIN, Pennsylvania — US President Donald Trump's announcement that he would double steel and aluminum import tariffs to 50 percent from this week drew ire from the European Union on Saturday, in the latest salvo in his trade wars.

The EU warned it was "prepared "to retaliate against the latest tariffs, adding that the sudden move "undermines ongoing efforts to reach a negotiated solution "between the bloc and the United States.

"We're going to bring it from 25 percent to 50 percent, the tariffs on steel into the United States of America," Trump said at a rally in Pennsylvania on Friday.

Shortly after, he posted on social media that the increased tariff would also apply to aluminum products and that it would take effect on Wednesday.

Canada's Chamber of Commerce quickly denounced the tariff hike as "antithetical to North American economic security".

"Unwinding the efficient, competitive and reliable cross-border supply chains like we have in steel and aluminum comes at a great cost to both countries," said the chamber's president, Candace Laing.

Australia's center-left government also condemned the tariff increase, with Trade Minister Don Farrell calling it "unjustified and not the act of a friend".

Since returning to the presidency in January, Trump has imposed sweeping tariffs on all trading partners. On Friday, he defended his trade policies, arguing that tariffs helped protect US industry.

However, economic experts said that bringing manufacturing jobs back to the US through aggressive tariffs is an unreachable goal.

"For the most part, Americans were not lining up for factory jobs," Nancy Qian, a professor of economics at Northwestern University in Illinois, told Xinhua News Agency, recalling that even during the pandemic, manufacturers struggled to retain workers.

Echoing concerns about the strategy's effectiveness, Robert Wiest, president of the Swiss-Chinese Chamber of Commerce, called the use of tariffs "a very crude tool".

He said the US trade policy is "definitely not very productive" and has failed to yield any results. Instead, it has created uncertainty and alienated not only allies but also important trading partners, he said.

Trump announced the higher tariffs just outside Pittsburgh, where he was talking up an agreement between US Steel and Japan's Nippon Steel.

He stressed that despite a recently announced planned partnership between the two companies, "US Steel will continue to be controlled by the USA".

Upon returning to Washington late on Friday, Trump told reporters he had yet to approve the deal.

A proposed $14.9 billion sale of US Steel to Nippon Steel had previously drawn political opposition from both sides of the aisle. Former president Joe Biden blocked the deal on national security grounds shortly before leaving office.