Katy Perry to Hillary Clinton: 'I'll write you a theme song!'

If Hillary Clinton ever needs a theme song for a potential presidential candidacy, Katy Perry's got it covered. 

Perry, 29, popped up at a signing for Clinton's latest book, Hard Choices, on Friday (june 20) and later posted a photo with the former US Secretary of State on Instagram.

Her caption: "I told @hillaryclinton that I would write her a "theme" song if she needs it..."

Clinton, 66, is seen by many as likely to throw her hat into the ring for the 2016 presidential elections, though she has not released an official statement yet. 

Perry, meanwhile, is likely to make good on her word, according to E! Online - she's politically active and has sung for Barack Obama and had lunch with Michelle Obama. 

Sources: E! Online, Instagram