Leo Burnett and Saatchi & Saatchi withdrew over what was said to have been SingTel's insistence that the winning agency should start work on the account as early as the beginning of January.
SingTel has responded by adding BBDO to the pitchlist, which also includes Bates Asia and Ogilvy & Mather.
Michael Rebelo, the Saatchis Singapore chief executive, said: "A pitch is a two-way process. It's not just the clients who are sizing up the agencies."
Kurt Viertel, the Burnett managing director, commented: "This was a very difficult decision."