LONDON (AP) — U.K.-based mining giant Anglo American has rejected a 31 billion pound ($39 billion) takeover offer from BHP Group, saying it significantly undervalues the company and its growth potential.

Anglo said Friday that its board unanimously rejected the “unsolicited” and “highly conditional” bid from BHP, which was announced a day earlier. The deal would create the world’s largest copper miner, with around 10% of global output — a hugely lucrative market as the world transitions to clean energy.

Anglo said in a statement to the London Stock Exchange that the BHP proposal is “opportunistic” and “fails to value” the company’s prospects.

“Anglo American is well positioned to create significant value from its portfolio of high quality assets that are well aligned with the energy transition and other major demand trends,” said chairman Stuart Chambers.