Read MoreRio Tinto CEO: China aiming for resource security
Rio issued the statement after Bloomberg reported that Glencore had talked to Rio's top shareholder, Chinese state-owned Aluminum Corp of China (Chinalco), to gauge its interest in a deal.
The report, citing people familiar with the situation, said talks with Chinalco took place in recent weeks, and Glencore was also testing the waters with other Rio shareholders, studying financial and regulatory obstacles as it weighed its next steps.
Any bid for Rio would need China's blessing, as Chinalco owns 9.8 percent of the company. Chinalco is sitting on a big loss on its stake, bought in February 2008 for 60 pounds a share, double Rio's current price, as it sought to block a $127 billion takeover bid from BHP Billiton.
Glencore, which last year bought rival Xstrata in the sector's largest ever takeover, has recently talked openly about wanting to merge with Rio Tinto, coveting its low-cost, high quality iron ore.
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But analysts and bankers saw major hurdles to a deal, saying Rio Tinto shareholders would want a massive premium, China would likely force a merged group to sell some copper assets, and Rio's conservative culture would clash with Glencore's aggressively entrepreneurial DNA.
Speculation has grown around a Glencore bid for Rio as prices of iron ore, which made up 92 percent of Rio's first-half profit, have slumped to five-year lows, as the top producers have flooded the market with new supply.
Rio has focused on slashing costs while expanding its iron ore output to what it calls "epic" proportions, not shying away from the fact that it is largely dependent on steel growth in China, which is slowing.
"The board believes that the continued successful execution of Rio Tinto's strategy will allow Rio Tinto to increase free cash flow significantly in the near term and materially increase returns to shareholders," Rio Tinto Chairman Jac Nasser said in a statement.