First Quantum Minerals has launched a C$5.1bn (£3.1bn) hostile takeover bid for copper and zinc producer Inmet Mining.
Vancouver-based First Quantum, which is listed in London and Canada, is offering C$72 for every Inmet share in cash and stock.
The company is taking its C$5.1bn cash and shares offer direct to Imnet's investors after two previous indicative approaches were rejected.
In late October, First Quantum approached Inmet indicating it was willing to pay C$62.5 a share for the company. About a week later, Philip Pascall, chief executive of First Quantum, approached Inmet with a part cash, part share takeover proposal pitched at $C70 a share.
Mr Pascall said First Quantum had NOW decided to go hostile after it "received a number of approaches from Inmet's key shareholders expressing their excitement about the potential for the combined company".
First Quantum is keen to get hold of Inmet's $6.2bn Cobre Panama project because a combination with First Quantum would create one of the largest copper miners in the world - with the potential to produce more than 1.3m tonnes of copper a year by 2018.
The cash component of First Quantum's offer will be financed through existing cash resources and a $2.5bn (£1.5bn) debt facility.