[Editor's note: This story was updated at 1:24 p.m. CT April 17.]
Billionaire activist investor Carl Icahn on April 16 nominated a five-person slate of his employees and business associates to replace the SandRidge Energy Inc. (NYSE: SD) board of directors, escalating his fight for control of the U.S. shale oil producer.
The move sets up a showdown at SandRidge's annual meeting later this year between the existing board and the hard-driving investor who has been trying to force the company to sell itself outright to either himself or another potential bidder.
Icahn has spent recent months blasting SandRidge's leadership, at one point accusing it of an apparent "disregard for any semblance of accountability."
He has successfully scuttled SandRidge's planned buyout of rival Bonanza Creek Energy Inc. (NYSE: BCEI) and forced the removal of the company's CEO and CFO.
Now, Icahn has set his sights on the company's board.
A SandRidge spokesperson said the company will be reviewing Icahn's proposed candidates and declined further comment.
Icahn, who waited until an April 16 deadline to nominate his slate, did not immediately respond to a request for comment.
Shares of Oklahoma City-based SandRidge, which produces oil in Oklahoma and Colorado, were off a penny at $14.64 in afternoon trading on April 16.
SandRidge's stock has lost nearly a third of its value since January, far below levels where Icahn first amassed his majority stake last fall.
Icahn had telegraphed earlier this month that he was likely to nominate directors. He has said he is willing to make an all-cash offer to buy the company.
SandRidge has not set a date for its 2018 shareholder meeting. The 2017 meeting was held in June. Most companies hold their annual meetings at the same time each year.
Icahn's slate includes current employees and employees or board members of companies he has controlled.
Icahn, who owns about 13.5% of SandRidge's float, nominated Jonathan Frates and Nicholas Graziano, both of whom work for the investor's companies.
The other three nominees are John Lipinski and Bob Alexander who have worked with refining company CVR Energy Inc., which is majority owned by Icahn, and Randolph Read, who has worked with investment fund Nevada Strategic Credit Investment.
Icahn has not always been successful in agitating for change at energy companies. In 2016, his hand-picked director at Chesapeake Energy Corp. (NYSE: CHK) resigned in what was widely seen as a tacit admission that the investor's turnaround strategy was not working fast enough.