PARIS — Rio Tinto, the global mining company that owns Kennecott Utah Copper, posted record first-half profits Tuesday, bolstering its effort to fend off a hostile takeover by BHP Billiton.

Rio Tinto said the results had been lifted by booming demand for iron ore from steelmakers in Asia and by the acquisition of the Canadian company Alcan for $38 billion in October.

Net income more than doubled in the period to $6.9 billion from $3.3 billion a year earlier. Revenue rose to $27.2 billion from $12.1 billion. Rio Tinto also raised its interim dividend by 31 percent to 68 cents.

The results Tuesday showed Rio Tinto's revenue from aluminum operations soared to $12.6 billion from $1.8 billion. The company did not break out the contribution of the Alcan deal to profit, but the chief executive, Thomas Albanese, said in a telephone interview that the acquisition had been "accretive to profit in the first half" and that "we haven't seen the full benefits of the acquisition yet."

Rio Tinto's underlying earnings, which exclude interest and taxes, rose to $5.5 billion in the first half from $3.53 billion in the period a year earlier. Analysts polled by Reuters Estimates had, on average, expected underlying earnings of $5.1 billion.

Shares of Rio Tinto, which have risen more than 54 percent in the last year, were down 0.56 percent, to 51.50 pounds, or about $95.80, in London.

The declines were part of a broad fall in mining stocks as commodity prices slipped. Baoshan Iron and Steel, the largest Chinese steel maker, said it would cut prices for some steel products on expectations that demand from automakers and appliance makers would slow. Resource-company investors are concerned that the slowdown in the global economy will weigh on raw materials prices.

BHP, which last week posted annual net income of $15.4 billion, wants to buy Rio Tinto to cut costs, obtain a bigger share of metals markets and increase its pricing power. It has offered 3.4 BHP shares for each Rio Tinto share, a bid that valued Rio Tinto at about $137 billion, based on the BHP share price Monday in London.

Rio's board has rejected the BHP offer as too low. Albanese said Tuesday in the telephone interview that the bid remained "a long way off" from what Rio Tinto believed to be a reasonable offer. He noted that Rio's top investors had been raising their stakes in the company, suggesting that shareholders "are comfortable with the position we've taken."

Tobias Woerner, an analyst at MF Global Securities in London, said BHP Billiton would need to raise its offer to win a deal, considering the strength of the recent earnings and Rio Tinto's growth potential.

"We've put a very compelling offer on the table," Alberto Calderon, chief commercial officer for BHP, said in an interview. "Nothing has changed" with Rio Tinto's strong first half.

Any combination would have to clear significant regulatory reviews in major markets.