The billionaire octogenarian is reportedly considering an offer to be an economics adviser under the president-elect, according to people familiar with the matter as reported by Fox Business.

It’s unclear whether Icahn would be in an official position in the White House or just an informal adviser—but since Trump won the presidential race Nov. 8, the billionaire investor has grown increasingly interested in an official position that would shape the country’s economic policy, sources told Fox.

The long-time Trump supporter has already been acting as an informal economic adviser to Trump’s presidential campaign. At one point, the investor was on Trump’s short list for Treasury Secretary, and even accepted the position in August 2015, before eventually declining the offer. Icahn also declined to officially join Trump’s campaign economic team, saying he would rather run his own business, Icahn Enterprises (IEP).

Cementing an advisery role, formal or informal, with the incoming Trump administration will likely allow Icahn to sway the president-elect on key issues they disagree on. For instance, while Trump has pledged to “dismantle Dodd-Frank,” Icahn doesn’t think a full on repeal of the law is the answer, according to an interview he gave to CNN. Icahn has also said he disagrees with Trump’s plans to end trade deals such as NAFTA.

Trump is already said to be considering a former Goldman Sachs (GS) banker, Steven Mnuchin, for the role of Treasury Secretary.

Fortune has reached out to Icahn and Trump’s transition team for comment. We will update this story when, and if they respond.