More than 30 labor contracts are due to be renegotiated next year - the largest number since 2010.
This means that nearly 40% of global copper production - or more than 7 million tonnes - could be subject to disruption due to industrial action next year, according to Barclays.
“This risk is largely concentrated in just two countries, Chile and Peru, and remains a crucial unknown factor for the market,” Barclays’ analyst Dane Davis said in a report.
While strikes are unlikely at more than a handful of mines, such risk should “add a significant premium to prices, even if the Chinese economy materially slows,” Davis added.
The average copper price on the London Metal Exchange in 2017 rose 26% year on year to nearly $6,150 per tonne.
For 2018, Barclays forecasts the annual average copper price at $6,175 per tonne, with a "significant degree of volatility" throughout the year.
Bank of America Merrill Lynch analyst Michael Widmer...