"Glencore was long the business that operated where others could not or would not," Hess said. "That seems like an increasingly untenable position." The US hasn't made any accusations of wrongdoing or specified what's it's investigating. Glencore said it's reviewing the subpoena and will provide further information as appropriate. Deripaska, Gertler Glasenberg in April had to quit the board of of one of Glencore's biggest aluminium suppliers, United Co. Rusal, after its main owner, Oleg Deripaska, was hit with the most punitive US sanctions imposed on a so-called Russian oligarch. Glencore's struggles in Congo, where it operates massive copper and cobalt mines, have also come under legal pressure, including a possible bribery investigation by British prosecutors over its work with Dan Gertler, an Israeli billionaire and close ally of Congo President Joseph Kabila, people familiar with the situation said in May.

But the US is casting a wider net with the addition of Venezuela and Nigeria to its investigation, increasing the likelihood that Glencore's management will get bogged down in a lengthy legal process. And any fines or charges that result will only further complicate internal efforts to settle on a successor to Glasenberg, 61. Glencore was long the business that operated where others could not or would not. That seems like an increasingly untenable position. Political risk analyst Maximilian Hess Glasenberg has run Glencore since 2002 and is also the company's second-largest shareholder, according to Bloomberg data. Two of his closest lieutenants are associated with legal challenges in the countries the Justice Department is focusing on. Glencore curbed the powers of Aristotelis Mistakidis, its head of copper, after a review of operations in Congo raised questions about accounting and management practices. And Alex Beard, Glencore's head of oil, was named in a 2015 lawsuit filed by a former representative in Nigeria. Christopher LaFemina, an analyst at Jefferies LLC, said the issue threatens to become a long-term drag on Glencore's shares, much like the ongoing dispute between rival miner Freeport-McMoRan and the Indonesian government.

"Investors are likely to assume Glencore will have to pay a large fine, and Glencore's cost of capital will increase due to increased risk in general," LaFemina said. Recovery threat Loading The revelation of the US probe is the latest in a string of headaches that have soured what should have been a triumphant moment for Glasenberg. Glencore's share price has more than quintupled from a collapse in 2015, when a commodity-wide downturn triggered a crisis of confidence in the company. It's been helped by a series of transactions that burnished Glasenberg's reputation as a shrewd dealmaker.

And Glencore's mines, particularly in Congo, which competitors such as Rio Tinto and BHP Billiton found too difficult to operate in, have given the company pole position in the race to supply metals that are vital to the emerging electric-vehicle market. Yet the African country has also been the source of most of Glencore's woes. Last year, Katanga Mining, a Congolese copper producer owned by Glencore, restated financial statements and announced an investigation by Canadian regulators for its corporate governance and accounting practices. Then in December, Gertler, the Israeli tycoon, was sanctioned by the US Treasury, which alleged he'd engaged in "opaque and corrupt" deals. Glencore has also been battling the Congolese government over a new mining code that hikes royalties and taxes, as well as dealing with lawsuits in the country from Gecamines, the state mining company, and Gertler. 'King of Oil' This isn't the first time Glencore has found itself in Washington's crosshairs. The company's founder, the late fugitive Marc Rich, was indicted in 1983 in part for trading oil with sanctioned Iran. Rich, who had been dubbed the "King of Oil", received a controversial pardon on former President Bill Clinton's last day in office in 2001.

That was a decade before Glencore first sold shares to the public, which made any future corporate missteps much more costly. "The fine is a tiny part of the damage this sort of thing does to a company," said Karina Litvack, former head of sustainable investment at F&C Asset Management. "Some of that damage can be quantified, but much of it cannot and this unquantifiable cost often dwarfs what can be easily measured." Bloomberg The US investigation is a blow to Glencore boss Ivan Glasenberg. Credit:Bloomberg