India, June 4 -- The United States doubled tariffs on imported steel and aluminium starting Wednesday, widening President Donald Trump's trade war in a move set to fan tensions with key economic partners.

The move, which Trump earlier said was aimed at protecting domestic steel and aluminium industries, takes his levies on both metals from 25 percent to 50 percent.

Trump cast the move, which took effect at 12:01 AM Washington time on Wednesday, as necessary to protect national security.

An order signed on Tuesday said the previous charge had "not yet enabled" domestic industries "to develop and maintain the rates of capacity production utilisation that are necessary for the industries' sustained health and for projected national defenc...