The United States doubled steel and aluminum tariffs Wednesday, casting a pall on a gathering of OECD ministers as President Donald Trump's intensifying trade war weighs on the world economy.

Trump's sweeping tariffs on allies and adversaries alike -- including levies on imported steel and autos -- have strained US ties with trading partners and sparked a flurry of negotiations to avoid the duties.

And pressure is mounting as the Organisation for Economic Cooperation and Development (OECD), a 38-nation grouping of mostly developed countries, cut its global growth forecast on the back of Trump's levies.

Trade, consumption and investment have been affected by the tariffs, OECD chief economist Alvaro Pereira earlier told AFP, warning that the US economy will see the biggest repercussions.

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