President Obama wished Vice President Biden a happy birthday over Twitter on Tuesday. His tweet included a photo of the two laughing over a shared joke. 

The tweet, however, was not signed "BO," which Obama adds when he personally posts to his Twitter feed.

Biden is 70 years old, but hasn't ruled out continuing his political career after a second term as vice president.

Asked by CNN last year if he had closed the door on a run for president in 2016, Biden replied that he was "not closing anything."