When "X-Men: Days of Future Past" director Bryan Singer announced that "X-Men" vets Ian McKellen and Patrick Stewart are officially coming back for the upcoming film, it apparently came as news to Stewart.

"Bryan let the cat out of the bag on Twitter, and it included announcing that Sir Ian and myself were going to be in this movie," he told EW, adding, "I know nothing about this project. And I'm hoping that might change in the future."

Stewart, who played Professor Xavier in the first three "X-Men" films (two of which Singer directed), explained that he is most definitely interested, but isn't officially on the "Future Past" team yet.

"I don't know that we're doing it," Stewart continued, somewhat cryptically. "I have not signed a contract yet. I know there is a project in development, but we have no dates. No detailed casting. Thrilled to hear that my dear friend and colleague Ian McKellen is on board, but I'm sorry, you know, you need to understand, I'm not being cute. I know nothing."

Previously, the former "Star Trek: The Next Generation" actor hinted about returning to the franchise. McKellen is reportedly excited to re-join the mutant movie series. Hugh Jackman is also in talks to once again appear as Wolverine.  
 
"X Men: Days Of Future Past" follows "X-Men: First Class" and takes place in two time periods. It will also star James McAvoy, Michael Fassbender and Jennifer Lawrence. 

It will begin filming in early 2013, and is scheduled to be released July 18, 2014.