Katy Perry did her bit for US President Barack Obama as she performed at one of his campaign events.

The Democrat is currently touring the country to encourage support ahead of the presidential election on November 6, where he will come head-to-head with Republican Mitt Romney.

Katy Perry has been a vocal supporter of Obama and she performed for him last night (October 24) at a rally in Las Vegas.

A crowd of 13,000 people turned up to support Obama and see Perry in action for a five song set, with the star wearing a dress telling people not to vote Romney.

The singer encouraged the young members of the crowd to use their vote wisely in the election, saying:

"Vote Early. Don't wait. Go tomorrow. How many of you are 18 here? It's going to be your first time, right?"

Birthday girl Perry tweeted soon after: "So tonight was a great night! The PRESIDENT gave grandma and I unforgettable shout outs & now I am officially 28! Best. birthday. ever."