The special relationship is between Clinton and former British Prime Minister Tony Blair.
Michael Sheen is set to play Blair. It would be the third movie for which Sheen has portrayed the British politician, along with "The Queen" and "The Deal." Sheen was also in "Frost/Nixon," written by Peter Morgan. Morgan will also write "The Special Relationship."
Spokeswoman Tobe Becker says HBO hasn't fully given the green light to the film, but is also working out a co-production deal with the BBC.