Matches have already been arranged with Seattle Sounders and Manchester United with one more fixture still to be confirmed.
“The Celtic F.C. match will replace the previously announced agreement with Valencia C.F.,” confirmed Philadelphia Union President Tom Veit.
“Unfortunately that game will not be played this year. Valencia and their appointed promoter have backed out of the agreement that was reached with the Union and other MLS teams.”
Philadelphia Union CEO & Operating Partner Nick Sakiewicz added: “Celtic has consistently been one of Europe’s top teams and we are very excited to round out our summer internationals with another one of Europe’s best .
“We are proud to treat our fans to such a high level of international football and expect a tremendous atmosphere for this match at PPL Park.”
Celtic Chief Executive Peter Lawwell said: “Celtic Football Club has enjoyed many successful visits to the United States and we are sure that our match in Philadelphia will be another great occasion
“We know Philadelphia Union is a fantastic club and is also drawing some great opposition in the form of Manchester United, so I am sure Union supporters will have some fantastic matches to look forward to this summer.
“We are a club which enjoys a magnificent backing worldwide and we are in the fortunate position of having many supporters across America. We are looking forward very much to meeting Philadelphia Union and hope on this visit to make many more new friends in the United States.”