MELBOURNE, March 2 (Reuters) - Premiums for aluminium metal in the United States spiked to the highest in almost three years after President Donalid Trump on Thursday flagged a 10 percent import duty, as buyers sought to secure metal before higher costs come into force.

Premiums are paid by buyers on top of exchange prices to cover insurance and the cost of delivery, and signal the strength of demand for physical metal,

Spot premiums for Comex aluminium jumped to 17 cents a pound ($375 a tonne) on Thursday, before finishing at 15.2 cents, up 12 percent from 13.6 cents the day before and the highest since April 2015.

President Donald Trump said on Thursday he would impose hefty tariffs on imported steel and aluminum to protect U.S. producers, risking retaliation from major trade partners like China, Europe and neighboring Canada as well as helping to trigger a large selloff on Wall Street.

(Reporting by Melanie Burton; editing by Richard Pullin)