The Phillies are in agreement on a three-team trade with the Mariners and Blue Jays to acquire star pitcher Roy Halladay, SI.com has learned. Sources say Halladay will agree to a contract extension to complete the deal. Cliff Lee will likely wind up with the Mariners in the deal. ESPN reported that the deal was close, but not yet done. Halladay would agree to a three-year extension through 2013, with a vesting option that could lengthen the deal by another year or two, one source said. Toronto would get highly regarded Mariners pitching prospect Phillippe Aumont, Phillies catching prospect Travis d'Arnaud and another Phillies prospect in exchange for Halladay. Indications are that the Phillies have balked at Toronto's repeated requests for outfielder Domonic Brown, and the Phillies are offering highly touted outfielder Michael Taylor instead. Seattle would send two additional prospects to Philadelphia in exchange for Lee, who is a year away from free agency.