NEW YORK/MELBOURNE (Reuters) - The U.S. securities regulator said on Monday that a U.S. court should deny a bid by Rio Tinto Plc RIO.LRIO.AX and two former top executives to have civil fraud charges over a failed African coal project dismissed.

FILE PHOTO - A sign adorns the building where mining company Rio Tinto has their office in Perth, Western Australia, November 19, 2015. REUTERS/David Gray/File Photo

The filing is the latest salvo in the SEC’s lawsuit accusing the defendants of waiting too long to write down the coal assets, enabling the big Anglo-Australian mining company to raise about $5.5 billion from U.S. investors.

“Defendants violated multiple provisions of the federal securities laws by engaging in a prolonged fraudulent course of conduct,” the U.S. Securities and Exchange Commission said in a filing with the U.S. District Court in Manhattan.

Accordingly, the defendants’ motion to dismiss the charges should be denied, it said.

The defendants are Rio Tinto, former Chief Executive Officer Tom Albanese and former Chief Financial Officer Guy Elliott.

In an emailed comment, a Melbourne-based Rio Tinto spokesman said: “Rio Tinto believes that the SEC case is unwarranted and that, when all the facts are considered by the court, or if necessary by a jury, the SEC’s claims will be rejected.”

Rio Tinto had acquired the coal assets in a 2011 takeover of Riversdale Mining and later renamed Rio Tinto Coal Mozambique for about $3.7 billion.

It wrote off most of the assets in January 2013 and sold them in late 2014 for just $50 million.

On March 5, the defendants said the SEC was “plainly wrong” to say they should have taken a big writedown no later than 11 months after the purchase.

They said rising prices for “scarce” coking coal offset lower barging and rail capacity, and might have even boosted the assets’ value at that time.

The SEC said that the defendants were wrong to argue that it was too soon to book an impairment on Rio Tinto Coal Mozambique (RTCM).

“Rio Tinto was required to assess impairment at every reporting period,” it said.

The defendants have until March 26 to respond, court records show. The case is being overseen by U.S. District Judge Analisa Torres in Manhattan.

On March 2, the Australian Securities and Investments Commission brought its own civil court action against Rio Tinto, Albanese and Elliott over the coal assets.