It noted a strike at the BHP-managed Escondida mine and Codelco's Andina mine would put about 5% and 0.9% respectively of global copper supply at risk.
Workers are set to vote on a contract offer in the coming days at Escondida, the world's largest copper mine, which has a history of labour action including a 44-day strike in the first quarter of 2017.
Andina workers have reportedly voted to strike and are set to walk off the job tomorrow, while a strike began this week after failed wage talks at Lumina Copper's Caserones mine, which Jefferies said represented 0.6% of global supply.
Analyst Christopher LaFemina said the medium/longer-term outlook for copper remained positive, due to a forecast "tsunami of supply" not eventuating and growing demand.
"We believe operating risk at many copper mines is elevated due to actions taken to maintain high volumes over the past 18 months despite COVID-related worker absenteeism," he said.
"Indeed, it is noteworthy that copper production from major miners was lower on a quarterly average basis in 1H21 than it was in 2020 despite the consensus view that a tsunami of supply would be coming this year in response to high prices.
"Our analysis indicates that global copper supply will continue to fall short of expectations, and a lack of supply growth should be positive for prices."
Copper hit a record high of US$10,747.50 per tonne on the London Metal Exchange in May.
Jefferies analysts said their positive view on copper was based on cyclical demand growth as the global economy continued to recover from the COVID-driven downturn of 2020, secular demand growth driven by EVs and decarbonisation policies in general, plus limited supply growth.
"We expect market deficits to lead to higher prices," LaFemina said.
"The key risk to this thesis is demand risk (macro, COVID), but we believe the copper mining equities are undervalued on a risk-adjusted basis."
Jefferies recommended buying Freeport-McMoRan, Glencore and First Quantum Minerals.