SANTIAGO, July 31 (Reuters) - Chile's Codelco, the world's top copper producer, said on Friday it boosted output by 4.7% in the first six months of 2020 even as the coronavirus outbreak forced it to rely on skeleton crews.

Pretax profits of $380 million jumped 20% over the year-ago period, the company said. Cash costs plunged 9%, helping boost profits alongside strong output.

"The early measures taken by the company to protect the health of its workers allowed us to maintain operational continuity," the company said in a statement.

Codelco said it produced 744,000 tonnes of copper in the first half, attributing the increase to improved processing, higher ore grades and resilience in the face of the pandemic.

Chile, the world's top copper producer, has largely maintained copper output despite the pandemic, with Codelco resisting union pressure to shut down its mines. (Reporting by Dave Sherwood and Fabian Cambero; editing by Jonathan Oatis and Richard Chang)