Commodity prices have fallen sharply since last summer
Anglo-Australian miner Rio Tinto has announced that China's state-owned Chinalco is to invest a further $19.5bn (Ł13.6bn) in the business.
The move - China's largest investment in a foreign company - could see Chinalco increase its stake in Rio to 18% from the current level of 9%.
The news came as Rio reported a 7% fall in 2008 profits to $9.2bn.
Global commodity prices hit record highs last summer before falling back sharply as the world economy slumped.
Rio said the fresh investment from Chinalco "creates a pioneering strategic partnership".
Paul Skinner: 'the governance of the company is not disturbed by this'
The deal will also allow Rio to reduce its debts, which are estimated at $39bn.
Chinalco's $19.5bn investment is made up of $12.3bn being spent on stakes in nine of Rio's mining assets, and $7.2bn on Rio bonds that can be converted into shares.
The announcement comes three days after Rio said non-executive director Jim Leng, who had been about to take over as chairman of the firm, had resigned.
Mr Leng quit after disagreeing with the board about how Rio should tackle its debt burden.
Some analysts questioned the timing of the deal, seeing as it comes at a time when commodity prices are low because of the weak global economy.
"Rio's board must be beside themselves having to do this," said Mark Pervan, senior commodities analyst at ANZ bank.
However, BBC business editor Robert Peston said this was only one way in looking at the announcement, and that in other respects Rio had got a good deal.
"Rio is securing a 60-year loan from the Chinese," he said.
"It's selling a right to buy its shares in the future at a massive premium to the prevailing share price."
Last year Rio rejected an informal $66bn takeover approach from rival BHP Billiton, which is also an Anglo-Australian company.
Rio also announced in December that it was cutting 14,000 jobs to reduce its debts by $10bn.