Until Tuesday, the global potash market was dominated by two cartels: the Belarusian Potash Company (BPC) and North America's Canpotex, the export arm of Potash Corp, Mosaic Co and Agrium Inc. BHP had tried unsuccessfully to take over Canada's Potash Corp in 2010.
BHP declined to comment on Tuesday. The company said as recently as last month that Jansen remained "an option."
Pushing ahead with Jansen would likely be taken negatively by investors eyeing BHP's spending, debt and dividend levels, according to analysts and industry sources. But a decision to scrap Jansen - in which BHP has invested $2 billion - means giving up what could be a crucial profit stream for future decades as developing countries begin to feed themselves better.
BHP, whose board was due to consider the project in the coming 12 months, has long said it saw the Jansen mine as a potential "fifth pillar," in addition to iron ore, copper, coal and petroleum.
The future of the project, though, has been in the balance since investors began to push companies to rein in spending last year, amid cooling commodities prices. Rivals have questioned the economics of Jansen and warned the mine could sink potash prices still deeper into the doldrums.
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"I don't know whether the project's going ahead or not. What I do know is the economics of that project don't work," Potash Corp Chief Executive Bill Doyle told Reuters last week.
"It's a negative return on investment and I don't know too many boards of directors that would approve a $14 billion project with a negative return on investment from Day One."
Uralkali on Tuesday predicted potash prices would fall below $300 a ton in the second half of 2013, from $400 now.
"This definitely puts Jansen on ice, because whoever puts it to BHP's board has to (do a) scenario analysis on pricing and no one is going to approve this project at prices of $300 a ton," said Colin Isaac, analyst with Atlantic Equities.
Jansen is the only remaining "mega project" for BHP - projects intended to capitalize on its low costs - after it shelved its $20 billion Olympic Dam mine last year and a plan for a new harbour to boost Australian iron ore exports.
"No scared cows"
For Mackenzie, named chief executive of BHP in February, the decision on Jansen will also be critical personally.
A Glasgow-raised geologist and academic, Mackenzie ran BHP's non-ferrous minerals division before taking on the top job. He has close ties to potash, having been the lead executive in BHP's ill-fated tilt for Potash Corp.
"It has to perform. It has to compete for a smaller amount of capital," Mackenzie said of Jansen at a presentation in May.
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Some analysts expect potash prices to rise over the longer term, and say that a wrong move on Jansen - which would not be producing before 2017 - could batter confidence in both BHP and its peers. Uralkali said in May that it would delay two of its potash mine expansion projects for as long as a decade if Jansen proceeds. Conversely, Mosaic said that it might reconsider its plans to scrap the remainder of its potash expansion if BHP cancels Jansen.
"The market is very myopic in terms of wanting just free cash flow and cash generation right now, instead of investment in projects," Sam Catalano, analyst at Nomura in London said. "If BHP approves what seems to be a marginal project, on the economics, the fledgling confidence investors have in the large miners to allocate capital will be shaken."
BHP could seek alternatives, such as keeping the Jansen option alive but postponing a decision on the project itself, or potentially taking on a partner - if one can be found.
The approved spend on Jansen is expected to run out over the coming months, but could be refreshed.
Goldman Sachs analysts last month estimated the need to approve the project could be deferred for another year at least, as the miner completes shaft sinking work, which reduces risks and could open up the option for BHP of selling a stake.
They, however, calculated a return of 10.3 percent - well below levels in an industry that favors 15 percent and above.