MTECHTIPS- Copper futures held steady near the strongest level since May 2015 on Tuesday, amid concerns over a disruption to global supplies after strikes at BHP Billiton (LON:BLT)’s Chilean Escondida and Freeport-Mc Moran(NYSE: FCX)’s Indonesian Grasberg mine. Combined, the mines produce roughly 10% of the world’s total copper supply. Copper for March delivery on the Comex division of the New York Mercantile Exchange dipped 0.2 cents, or around 0.1%, to trade at $2.781 a pound by 8:20 AM ET (13:20 GMT), after rising 1.5 cents, or about 0.6%, a day earlier. Nymex copper rallied to $2.823 on Monday, the most in 20 months. Meanwhile, three-month copper on the London Metal Exchange shed 0.2% to $6,113.25 a metric ton after rising to $6.202.25 in the prior session. Workers at the Escondida mine in northern Chile have been on strike since last Thursday after talks between management and workers broke down. The workers union has warned that the strike could be lengthy, potentially affecting global supplies.