A senior official of Chinese metals group Chinalco has spoken out against suggested changes to its planned $19.5bn investment in Rio Tinto, despite growing signs that concessions may be needed to secure the support of Rio's other shareholders.

In an interview with the Financial Times, Wang Wenfu, president of Chinalco Overseas Holdings, dismissed demands by some Rio shareholders to be given the same opportunity as Chinalco to buy convertible bonds. “This investment is a package. It is a result of two months of very intensive negotiations. It cannot be viewed separately,” he said.

Chinalco wants to invest $7.3bn in convertible bonds that would increase its equity stake in Rio from 9 to 18 per cent. It is also planning to pay Rio $12.3bn for minority stakes in some of the mining group's best operations.