WASHINGTON (Reuters) - Several Democratic senators pressed billionaire investor Carl Icahn on Monday to clarify his role as an adviser to President Donald Trump, saying his position in the administration raised “alarming” questions about potential conflicts of interest with his stakes in the biofuels and pharmaceutical industries. The senators, led by Sheldon Whitehouse of Rhode Island, sent a letter to Icahn pointing out that, as a Trump adviser on regulation, he has made policy proposals that benefit his own investments - which range from an oil refinery to an nutritional supplement manufacturer. “We write because we are increasingly concerned about the role you are playing in the Trump Administration and the possibility that you are breaking federal conflict of interest laws,” the seven senators wrote in the letter, seen by Reuters. Calls to Icahn’s office and lawyer were not immediately answered.  Icahn has been thrust into the limelight in recent weeks after the Renewable Fuels Association said he had informed them that Trump was preparing an executive order to overhaul the U.S. biofuels program in a way that benefited refiners. The White House quickly denied it had an executive order in the works, and pointed out that Icahn held an informal, unpaid role as adviser to Trump.  The senators said that despite the administration downplaying his role, Icahn has disclosed to the Securities and Exchange Commission (SEC) that he was a special adviser, meaning it is important to shareholders of the companies in which he holds stakes in.  Icahn owns an 82 percent stake in CVR Energy, which along with other refining companies, has called for changes to the Renewable Fuel Program to shift the burden of blending biofuels into gasoline away from refiners and further down stream to marketers. Icahn has said the change would help the entire refining industry, not just CVR.  Icahn also owns stakes in Herbalife and Bristol Meyers-Squib. The senators said Icahn had helped Trump pick the heads of the Treasury, Commerce, and the SEC, which have some oversight over the companies in which he has a stake. “Your ownership of each of these companies – and others – raises alarming questions about how you, and the Trump Administration, are handling your many conflicts of interest,” the senators wrote. In their letter, the senators said Icahn should be re-classified by the Trump administration as a special government employee, making him subject to ethics requirements.  When Trump announced in December that Icahn would be a special adviser, Trump made clear he would “not be serving as a federal employee or a Special Government Employee and will not have any specific duties.” The letter also includes over a dozen questions about Icahn’s ties to the administration, including whether he has received waivers from ethics requirements, and whether he has divested from some of his financial holdings.     