(Sharecast News) - Shares in Antofagasta came under pressure in early trading on Wednesday, after the Chilean miner warned annual production would be at the lower end of guidance.

Updating on second-quarter trading, the London-listed firm said copper production was 155,300 tonnes, up 20% year-on-year.

The increase was driven by its Los Pelambres mine, following an extended concentrate pipeline maintenance and cleaning activities required in February.

However, it was offset by lower grades and recoveries at the Centinela mine's concentrator, related to elevated levels of clay and fines in ores processed.

As a result, copper production in the first half was 284,700, down nearly 4% year-on-year, with total production for 2024 now expected to be at the lower end of the company's guidance for between 670,000 and 710,000 tonnes.

As at 0815 BST, the blue chip was down 3% at 2,054p.

Ivan Arriagada, chief executive, said: "Through our consistent investment throughout the commodity cycle, we have delivered growth a built a portfolio of high-quality, long-life operations.

"At Centinela, construction work is progressing ahead of schedule at the second concentrator project. At Los Pelambres, the phase 1 expansion project has successfully ramped up to nameplate capacity.

"Taken together, these investment will add both growth and long-term security to the future of our portfolio."