The Oscar-winning Milk star is in discussions to portray Plame's husband Joseph Wilson in Doug Liman's movie. The director had previously sought Nicole Kidman and Russell Crowe for the two lead roles.
The movie is based on Plame's memoir Fair Game: My Life As A Spy, My Betrayal By The White House.
Former politician Wilson saw his wife Plame (Watts) dismissed from the CIA after 20 years of service when she accused the Bush administration of lying about weapons of mass destruction in her Washington Post column.
The pair filed a civil suit against former Vice President Dick Cheney, Karl Rove and ex-chief of staff Lewis Libby when her covert status was compromised. Rove and Deputy Secretary of State Richard Armitage later admitted that they leaked her CIA links to journalists.