Icahn reportedly holds an 82-percent stake in the Sugar Land, Texas-based company, acquiring a controlling interest in 2012.
Icahn's involvement with Trump has frequently come under criticism from Democrats who, in May, asked USA regulators to investigate Icahn's activities in the US biofuels blending credit market.
Scores of Republican politicians and business leaders have distanced themselves from the president after his comments following the terrorist attack in Charlottesville, with the president's business advisory councils choosing to disband, and former Republican elected officials Mitt Romney and Arnold Schwarzenegger blasting Trump's excuse-making for participants in a march that attracted neo-Nazi and white supremacist elements.
Icahn said in a letter to Trump released Friday that he would resign to prevent "partisan bickering" about his role that Democrats suggested could benefit him financially. The activist investor earlier had pushed for a break up of the insurer in order to help it escape its regulatory tag as "too-big-to-fail", but eased his demands this year.
"As I know you are aware, the answer to that question is an unequivocal no, for the simple reason that I had no duties whatsoever", Icahn wrote in his letter to Trump. Icahn is one of the top five shareholders of AIG.
Saints starting CB Delvin Breaux to miss 4-6 weeks after misdiagnosis
Mike Triplett , with ESPN , then reported Wednesday that the team learned Breaux had apparently suffered a fractured fibula . The New Orleans Saints have finally figured out what has been taking so long for cornerback Delvin Breaux to heal.
Icahn's departure followed a flurry of changes at the White House.
"Following his apparent failure to win a regulatory change on ethanol rules that would benefit his personal empire, Carl Icahn is taking his ball and going home", Robert Weissman, the president of the nonprofit advocacy group Public Citizen, said Friday.
Moreover, Bloomberg reported, Democratic Senators Elizabeth Warren and Sheldon Whitehouse sent a letter in July asking Treasury Secretary Steven Mnuchin about Icahn's potential role in a regulatory decision that affected American International Group Inc.
Prior to being named a special adviser in December, he had backed many of Trump's campaign ideas.
As an adviser to Trump, Icahn urged the president in February to alter the policy to lift the blending burden from refiners.
A message left for Icahn's spokeswoman wasn't immediately returned. I truly appreciate the confidence you have in me and sincerely hope that the limited insights I shared have been helpful to you. "I sincerely regret that because of your extremely busy schedule, as well as my own, I have not had the opportunity to spend almost as much time as I'd hoped on regulatory issues", Icahn wrote.