Rio Tinto Plc (RIO) on Tuesday said a U.S. regulator's lawsuit...

Rio Tinto Plc (RIO) on Tuesday said a U.S. regulator's lawsuit accusing the big Anglo-Australian mining company of fraud for overstating the value of Mozambique coal assets it had bought in 2011 should be dismissed.

In a letter filed with the U.S. District Court in Manhattan, a lawyer for Rio Tinto said the U.S. Securities and Exchange Commission failed to plead that the company intended to commit fraud or made false statements related to asset values. He also said Rio Tinto was not required to write down assets sooner.

Similar letters were also filed by lawyers for former Chief Executive Officer Thomas Albanese and former Chief Financial Officer Guy Elliott, who were also targets of the SEC's civil fraud lawsuit filed last Oct. 17.

Albanese "at all times conducted himself in the manner expected of any reasonable CEO," while Elliott "relied on a well-tested and rigorous process" to ensure the proper reporting of Rio Tinto's financials, their respective lawyers said.

Representatives of the SEC did not immediately respond to requests for comment.

The SEC had accused Rio Tinto, Albanese and Elliott of concealing the deteriorating value of assets at Rio Tinto Coal Mozambique, which the company bought for $3.7 billion in April 2011 and sold three-and-a-half years later for $50 million.

According to the SEC, Rio Tinto hid the deterioration while it was raising $5.5 billion from U.S. investors, including $3 billion after executives in Mozambique had told Albanese and Elliott that their subsidiary likely had a negative net worth.

Rio Tinto wrote down most of the assets' value in January 2013, reducing it to $611 million, the SEC said.

The SEC filed its lawsuit on the same day the UK Financial Conduct Authority said Rio Tinto would pay a 27 million-pound ($37 million) fine to settle claims that it breached accounting rules related to the Mozambique assets.

Tuesday's letters set forth arguments that lawyers for Rio Tinto, Albanese and Elliott said they expect to make at a later date, when they formally seek the dismissal of the SEC case.

($1 = 0.72 British pound)