The war of words has been incrementally ratcheting up since BHP first approached Rio with a takeover offer last year.
In the wake of the two companies' third-quarter production figures matters are heating up.
Yesterday, just before BHP released its production figures for the March quarter and the first nine months of the 2007-2008 financial year, BHP boss Marius Kloppers delivered a stinging attack on Rio Tinto via the pages of the Financial Times newspaper in the United Kingdom.
"Tom Albanese has been comprehensively outperformed (by BHP) in terms of volume growth, earnings per share growth, total return for shareholders and share price performance," Kloppers said.
"They have missed the boat on China, they are missing the boat on energy. It must be terrible that, every quarter, BHP outperforms and that has been the case for seven years."
His comments follow on from Rio chief executive Tom Albanese's remark last week that BHP's petroleum business was too small to matter, and Rio's position in iron ore was much more significant.
This morning, Albanese and Rio chairman Paul Skinner again used the company's shareholder meeting in Brisbane to talk up the company's growth prospects.
Skinner told shareholders the company is still arguing for the freight differential with Asian iron ore buyers, and the price Vale agreed to earlier this year was simply not good enough.
Albanese, meanwhile, said the company was now targeting $US1.1 billion in synergies from the Alcan acquisition, up from original targets of $600 million.
While neither said anything materially different from their presentations in London last week, BHP's strong production growth across iron ore is considered to have put Rio on the back foot for now.
Yesterday BHP reported record iron ore production levels for both the year to date and the March quarter from its Pilbara operations and the Samancor project in Brazil.
BHP's production for the first nine months of the year was 13% higher than in the same period in the last financial year, and the March production level of 28 million tonnes was up 1% on the company's production for the three months to December.
While Rio produces significantly more of the bulk commodity than BHP, Rio reported a fall in iron ore production across all of its operations from 38.96Mt in the December quarter of last year to 37.37Mt in the three months to March.
Iron ore isn't the only commodity in the game, of course, but with both companies struggling with copper production.
In copper, BHP reported a drop in red metal production on a quarterly basis of 6% to 328,900t, undermining the company's year-to-date production record of 984,800t, up 8% for the nine months of the 2007-2008 financial year compared to the same period in 2006-2007.
Rio's copper production, meanwhile, was hit by reduced grades from Kennecott copper in Utah and the Northparkes mine in New South Wales, and its share of refined production fall from 89,000t quarter-on-quarter.
Total copper production rose from last year's fourth quarter figure of 180,900t to 185,600t, but both copper production and refined copper production fell from the corresponding period in 2007.
In coking coal, another key commodity enjoying a boom, both companies have been hit hard by adverse weather in Queensland, but analysts generally agree BHP's position is stronger.
Rio's position in aluminium, via the Alcan acquisition last year, and BHP's petroleum division, are shaping as the key points of difference between the companies, with iron ore acting as the major yardstick.
But with BHP still working on necessary approvals to officially table its offer to Rio's shareholders, the war will be continue for quite some time.
Shares in BHP fell 40c to $44.70 this morning while Rio was down 81c to $146.38.
