Washington, March 8 (AFP/APP) : US President Donald Trump on Thursday signed off on deeply contentious trade tariffs, swatting aside warnings of a global trade war and protests from allies in Europe and at home.

Trump has approved levies of 25 percent on imported steel and 10 percent on imported aluminum, with the measures coming into effect in 15 days, the White House said.

The tariffs will not apply to Canada and Mexico initially, an official said, adding that security and trade partners could negotiate to avoid the measures coming into effect.