Aluminum Corp of China (Chinalco) confirmed yesterday it had taken up its full entitlement in Rio Tinto's US$15.2 billion rights offer and said it would continue to monitor developments at the global mining giant. The subscription, which cost the Beijing-based company about US$1.5 billion, enabled it to maintain its 9 per cent stake in Rio. 'This was an economically rational decision, as it prevented the dilution of our ownership in Rio,' a Chinalco spokesman said. The two companies' relationship soured last month after Rio walked away from a US$19.5 billion tie-up with Chinalco and instead chose the rights issue and the establishment of an iron ore joint venture with rival BHP Billiton. Chinalco's move underscored the company's determination to maintain ties with the world's second-biggest iron ore miner, analysts said. 'Chinalco believes in the long-term prospects of the industry and will continue to explore opportunities to advance its strategic objectives,' the spokesman said, adding that the company, as Rio's largest single shareholder, would continue to monitor developments at the miner. On June 5, Rio announced plans to raise US$15.2 billion through a rights issue, on the basis of 21 existing shares for 40 rights shares, to help pay the huge debt incurred in the acquisition of Canada's Alcan in 2007. The dual-listed company said yesterday the British tranche of the rights issue was 97 per cent subscribed. Results from the Australian offer will be announced today. The rights shares were priced at a steeply discounted A$28.29 per Australian-listed share and GBP14 per London-listed share. Rio's Australian shares closed at A$51.75 yesterday, while its London shares closed at GBP21.58 on Wednesday. Brokerages expect Rio's gearing to drop to about 37 per cent after the rights issue, from 61 per cent. Chinalco bought its stake in Rio in February last year, near the peak of the market, at GBP60 a share. By buying the rights shares, it will lower the average cost of its holding. Despite suffering the setback of the failed Rio deal, Chinalco president Xiong Weiping said earlier that the strategy of becoming a leading global diversified resources company would not change. Shortly after the end of the proposed Rio alliance, the market speculated that Chinalco would turn its attention to Australia's third-biggest iron ore producer Fortescue Metals Group and Anglo-American, a diversified mining and natural resources group.