US President Donald Trump has defied opposition from the Republican party and protests from global allies as he signed orders imposing stiff and sweeping new tariffs on imported steel (25 percent) and aluminium (10 percent), media reports said.
"The actions we are taking today are not a matter of choice; they are a matter of necessity for our security," Trump said in a ceremony at the White House on Thursday evening where he officially authorised the tariffs, which will go into effect in 15 days.
Thursday's move comes after a week of furious lobbying and a burst of last-minute internal debates and confusion, reports The New York Times.
For now, Trump agreed to exempt, Canada and Mexico and held out the possibility of later excluding allies like Australia.
Flanked by a handful of steel and aluminium workers, Trump presented the move as a way to rebuild vital industries decimated by foreign competition.
"Our factories were left to rot and to rust all over the place; thriving communities turned into ghost towns... That betrayal is now over," The New York Times quoted the President as saying.
"This is not merely an economic disaster, but it's a security disaster we want to build our ships, we want to build our planes... with steel and aluminium from our country.
"We're finally taking action to correct this long overdue problem. Today I'm defending America's national security by placing tariffs on foreign imports of steel and aluminium," he added.
Trump is imposing the tariffs using a rarely employed trade provision known as Section 232 of the Trade Expansion Act of 1962, claiming a national security rationale for protecting the domestic steel and aluminium industries, reports CNN.
The President's move is expected to be questioned and countered, and could further put the US at odds with the international community.
Coming on the same day that 11 US allies -- but not the US -- sign a landmark Asia-Pacific trade agreement, the move on tariffs only underscores Trump's embrace of the protectionist policies he believes helped him win the presidency.
He also faced continued criticism from his Republican party, most notably House Speaker Paul Ryan who continued to lament Trump's move.
"I am pleased that the President has listened to those who share my concerns and included an exemption for some American allies, but it should go further. We will continue to urge the administration to narrow this policy so that it is focused only on those countries and practices that violate trade law," CNN quoted Ryan as saying on Thursday night.
"Our economy and our national security are strengthened by fostering free trade with our allies and promoting the rule of law."
The US is the largest steel importer in the world and the order could hit South Korea, China, Japan, Germany, Turkey and Brazil the hardest.
In 2002, former President George W. Bush had imposed steel tariffs of up to 30 per cent, The New York Times reported.
But facing an adverse ruling by the World Trade Organization and retaliation by trading partners, he lifted them 15 months before the end of the planned three-year duration.
Studies found that more jobs were lost than saved and Republican leaders vowed not to repeat the experiment.