Chairman and CEO Philip Pascall said the copper market had "excess demand" but the company wanted to ensure a certain level of cash flow during Cobre Panama's commissioning and ramp-up phases.
"While metal prices are being negatively affected by global political concerns, demand for copper remains robust," he said.
"Nevertheless, in light of current conditions, we think it is prudent to extend our copper sales hedge programme on a limited basis."
It extended the programme to cover 25,000t of forward sales contracts at an average $3.15/lb with maturity to December 2018, and 98,000t at $3.04-$3.45/lb with maturities to June 2019.
First Quantum said its majority-owned Cobre Panama development project had achieved key milestones during the quarter towards phased commissioning in 2018, including beginning first commissioning activities at the process plant.
Cobre Panama is expected to produce 330,0000-350,000t in 2021, its first full year of ramped-up production.
The company announced net earnings attributable to shareholders of $135 million and declared a C$0.005 per share interim dividend for the year ending December 31.
It reported record quarterly copper sales of 152,403 tonnes - with a 28% production increase from its Sentinel mine in Zambia and maintenance deferred at Las Cruces in Spain - and an all-in sustaining cost of $1.76 per pound.
First Quantum said it had provided relevant documentation to the Zambia Revenue Authority to rebut an $8 billion tax bill and said it remained engaged with the agency and "committed to ensuring transparency in all discussions between the parties".
It ended the quarter with $682 million in unrestricted cash and equivalents.
Its shares have ranged between C$12.09-$23.05 over the past year and closed 8c higher at $19.13.