The world's second biggest miner vowed to "vigorously" defend the allegations, while announcing it had separately settled a case with Britain's Financial Conduct Authority about the timing of writing down the same projects.
Under that arrangement, Rio was fined 27.35 million pounds (US$36 million) for breaching disclosure and transparency rules by failing to carry out an impairment review in a timely manner.
The US complaint was filed by the Securities and Exchange Commission in a Manhattan court, Rio said, with the miner, former chief executive Tom Albanese and ex-chief financial officer Guy Elliott facing claims they failed to follow accounting standards and company policies.
Albanese ultimately lost his job over the issue.
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The SEC contends the company failed to accurately value the acquisition and hid or delayed disclosure of the mounting losses.
"As alleged in our complaint, Rio Tinto's top executives allegedly breached their disclosure obligations and corporate duties by hiding from their board, auditor, and investors the crucial fact that a multi-billion dollar transaction was a failure," said the SEC's co-director of its Enforcement Division Stephanie Avakian.
"They tried to save their own careers at the expense of investors by hiding the truth."
Rio Tinto plc, Rio Tinto Limited, Albanese, and Elliott are charged with violating the antifraud, reporting, books and records and internal controls provisions of US federal securities laws.
The regulator is seeking injunctions, a return of "allegedly ill-gotten gains plus interest", and civil penalties. It also wants Albanese and Elliott banned from serving as public company officers or directors.
Both took place under Albanese's leadership.
It claims the African asset failed as it was based on the incorrect assumption that Rio could inexpensively mine, transport, and sell large quantities of high-quality coal, chiefly using barges for shipping.