* Seeks $20 bln market capitalisation by end-2020 * Plans $6.5 bln overseas capex to 2018 WARSAW, Feb 11 (Reuters) - Polish copper miner KGHM plans to spend 20 billion zlotys ($6.5 billion) on its foreign assets by 2018 to almost double its market value by the end of the decade, the company said on Monday. The $12.2 billion state-controlled company, Europe's second-biggest copper producer, started its overseas expansion plan last year with the C$3 billion ($3 billion) purchase of Canada's Quadra FNX, now named KGHM International. The Canadian acquisition, comprising the Chilean Sierra Gorda copper project and other assets in Chile, Canada and the United States, adds to the company's other Canadian operation in the Afton-Ajax project with Abacus Mining. "We're one third of the way on our road to becoming a fully global company, valued at about $20 billion," KGHM Chief Executive Herbert Wirth said, adding that it wants to achieve this by the end of 2020. "Our first milestone will be the 2014 launch of our largest mine (in Sierra Gorda, partnered by Sumitomo Metal Mining ). The second will be the Victoria project in Canada in 2016 and the third is Afton-Ajax in British Columbia in the same year." KGHM, which is also the world's No.1 silver producer, is targeting annual copper output of 700,000 tonnes by 2018. The company said on Monday that it expects copper production from its Polish mines to total 562,000 tonnes this year. A report by consultancy Micon said that KGHM's Polish mining reserves stand at nearly 1.2 billion tonnes, comprising 18.6 million tonnes of copper and 1.8 billion ounces of silver - sufficient to sustain operations for at least 30 years. "1.2 billion tonnes of mineral reserves place KGHM in the world's top five players," Micon analyst Christopher Lattanzi told a news conference in Warsaw.