(Bloomberg) — Anglo American Plc rebuffed a sweetened takeover offer from BHP Group Ltd. that valued it at about £34 billion ($43 billion), leaving it up to the Australian miner to make a better bid or lose out on what could be the industry’s biggest deal in a decade.

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BHP, the world’s largest miner, is seeking to buy Anglo for its South American copper assets. That would make it the No. 1 copper producer, alongside its sprawling portfolio of iron ore and coal. BHP’s initial approach was rejected by Anglo.

BHP said Anglo rejected its latest offer, which was 15% higher than its first approach, on Monday. The new proposal — tabled on May 7 — still included the stipulation that Anglo must spin off its South African units before the acquisition. Anglo has dismissed that structure.

The pressure is now on Anglo to show shareholders how it can deliver more value on its own, while BHP will need to improve its offer again for a deal to happen. Top executives of both companies are at a conference in Miami this week.

Read More: Anglo Investors Tell Company to Move Faster to Survive BHP Bid

If successful, a takeover would mark a return to large-scale dealmaking for BHP, which has revived its appetite for transformational acquisitions in the past couple of years under Chief Executive Officer Mike Henry.

“BHP put forward a revised proposal to the Anglo American Board that we strongly believe would be a win-win for BHP and Anglo American shareholders,” Henry said in a statement on Monday. “We are disappointed that this second proposal has been rejected.”

BHP presented its own vision for Anglo: separate two South African businesses and buy the rest, including the company’s copper mines, its crown jewels.

Read More: What’s Anglo Worth? For Now It’s Less than the Sum of Its Parts

BHP, which has a market value of about $145 billion, has made copper a central part of its strategy, betting that supply will struggle to keep pace with demand for metal to build electric vehicles, solar panels and high-voltage cables. But the company’s expansion options at its own assets are not enough to offset its retreat from fossil fuels, creating pressure to add new mines from outside.

A successful takeover would make BHP the biggest copper producer with about 10% of the market. The offer is also sparking predictions that it will set off a wider wave of mining M&A, with many of BHP and Anglo’s rivals scouting for their own copper deals.

Anglo shares fell 0.5% as 2:15 p.m. in London, while BHP’s London traded shares dropped 0.4%.

(Updates with details throughout.)

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