Corporate raider Carl Icahn, 80, considered instrumental in forcing major changes at U.S. energy companies -- including Chesapeake Energy Corp. and Freeport-McMoRan Inc. -- has been tapped by President-elect Trump as a special, unpaid adviser to help overhaul "job-killing" regulations.

The Trump transition team has promised to overhaul energy and environmental rules put in place by the Obama administration.

"Carl was with me from the beginning and with him being one of the world's great businessmen, that was something I truly appreciated," Trump said. He is "not only a brilliant negotiator, but also someone who is innately able to predict the future especially having to do with finances and economies. His help on the strangling regulations that our country is faced with will be invaluable."

The billionaire is expected to advise Trump in an individual capacity and would not be a federal employee or a special government employee. Icahn "will not have any specific duties," the transition team said. According to reports, Icahn already has offered his advice on the Interior Department pick, Montana Republican Rep. Ryan Zinke. Icahn also is to have input on the new head for the U.S. Securities and Exchange Commission, according to reports.

Icahn's net worth is estimated at $16.5 billion, according to Forbes. He long has used his financial wherewithal to force energy sector companies to bend to his wishes.

Icahn became Chesapeake's second-largest shareholder in 2010 as the onshore producer struggled with finances and mismanagement. He was considered instrumental in forcing out board members and eventually, CEO Aubrey McClendon in 2013.

In 2015, Icahn acquired an 8.46% stake in offshore operatorFreeport-McMoRan, which has since undergone a major overhaul. Late last year Icahn issaid to have been instrumental in ousting Cheniere Energy Inc. CEO and co-founder Charif Souki.

Icahn and affiliates also have been considered key in helping to force management changes at, among others, Talisman Energy Inc., now owned by Repsol SA, along with Dynegy Inc., as well as Anadarko Petroleum Corp. and predecessor companies.

As well, Icahn has major holdings in other energy enterprises, including an 80% stake in refining giant CVR Energy Inc., which has unconventional oil and gas-related infrastructure developments across the U.S. onshore.

Following the announcement, Icahn took direct aim at the Obama administration.

"Under President Obama, America's business owners have been crippled by over $1 trillion in new regulations and over 750 billion hours dealing with paperwork," he said. "It's time to break free of excessive regulation and let our entrepreneurs do what they do best: create jobs and support communities."

In an interview with The Wall Street Journal Wednesday, Icahn said, "What Trump is trying to achieve is to show business in a lot of this country they aren't going to be ruined by absurd regulation by bureaucrats."