Fannie Mae ( FNM) CEO Herb Allison is expected to be named by the Obama administration to head the government's $700 billion Troubled Asset Relief Program, a report says. Allison is the former chairman of investment company TIAA-CREF and served as president and chief operating officer at Merrill Lynch. He agreed to run Fannie Mae in September after the U.S. took over it and Freddie Mac ( FRE). President Barack Obama could announce his intention to nominate Allison as assistant secretary for the Office of Financial Stability as early as this week, the Wall Street Journal reports. Allison would replace Neel Kashkari, a holdover from the Bush administration, who was asked by Treasury Secretary Timothy Geithner to stay on until a replacement was found. Allison's selection would leave Fannie Mae and Freddie Mac without chief executives. David Moffett, Freddie Mac's CEO, resigned in March. Allison has been on the shortlist to head TARP from the beginning, the Journal reports. His selection was complicated by several factors, including the need to replace him at Fannie, the Journal adds, citing people familiar with the matter.