BHP Group has just hours to launch a blockbuster bid to buy smaller mining rival Anglo American — or put its audacious takeover plan on the shelf.

The proposal by the world’s biggest miner to spin off two units and then buy the remainder of Anglo would create a global copper behemoth, heralding the industry’s return to mega—deals after more than a decade. Anglo has already rejected two non-binding offers from BHP — the last worth $43-billion — and unveiled its own plans for a radical restructuring.