The Wall Street Journal quoted an internal Citigroup memo saying that Alexander would leave his job in Citi to work on domestic financial issues at the Treasury, which is facing staff shortage.
Lewis Alexander, who has been at Citigroup since 1999 and before that worked at the Federal Reserve, will head to the Treasury "to work on domestic financial issues", the memo stated.
Further, the WSJ report cited a government official as saying that Alexander would be a counsellor to Treasury Secretary Timothy Geithner.
However, Alexander and a Treasury spokesman were not available for comment, while a Citigroup spokesman declined to elaborate on the memo.
Alexander, who was the commerce department's chief economist from 1993 to 1996, is joining the Treasury at a time when the department is desperately trying to fill up the vacancies for senior posts.
The staff shortage has fostered doubts on Wall Street and in Washington about the Obama administration's ability to get a grip on the financial crisis, it added.