Arnold Schwarzenegger told Sen. John McCain "you'll be back," in a tweet on Thursday after McCain was diagnosed with brain cancer.

"You're right - you'll be back. You have to be back. We need your straight talk, your strength & your courage. I'm thinking of you, my friend," Schwarzenegger said.

Schwarzenegger, an actor and former Republican governor of California, responded to McCain's tweet thanking everyone for their support. "I greatly appreciate the outpouring of support - unfortunately for my sparring partners in Congress, I'll be back soon, so stand-by!" McCain tweeted Thursday.

You're right - you'll be back. You have to be back. We need your straight talk, your strength & your courage. I'm thinking of you, my friend https://t.co/BvVhStVvyG — Arnold (@Schwarzenegger) July 20, 2017

Schwarzenegger's tweet was playing off his famous line, "I'll be back," from the movie "Terminator" to encourage McCain who said that he will return to Congress soon.

McCain's office on Wednesday revealed that the senator has brain cancer. After an operation in Phoenix to remove a blood clot from above his left eye it was determined by tissue extracted during the procedure that McCain had brain cancer.

There has been an outpouring of bipartisan encouragement for the longtime senator and former presidential candidate with many calling the 80-year-old a "fighter."

McCain received treatment at the Mayo Clinic Hospital in Phoenix. A statement from the hospital said that treatment options "may include a combination of chemotherapy and radiation."