Beyonce Backs U.N.'s World Humanitarian Day: Watch Now!

Singer will film live music video for 'I Was Here' to support campaign.

Last week, Beyoncé posted a mysterious message on her website that simply read, "Leave your footprint on 19 August 2012."

The cryptic note had many fans wondering just what Queen B might be up to come mid-August. Well, the answer is here, and Beyoncé not only wants her Beyhive to leave their footprint that day, but she'll also be doing the same.

The superstar has joined forces with the United Nations and humanitarian aid organizations for World Humanitarian Day on August 19. It is "a global day to celebrate humanity and the spirit of people helping people," according to a press release.

The VMA-nominated singer will be in New York City for the big celebration, along with her "I Was Here" songwriter, Diane Warren. The ladies will be on hand at the U.N. General Assembly Hall to film a live music video for the 4 ballad that they will then donate to the cause. It will be released that same day.

Beyoncé appears in a black-and-white PSA for the campaign. A close-up of her face, sporting the braids she debuted a few weeks back, shows her outdoors. "It's high time we rise together," she says. "Do one thing for another human being — nothing is too small. It begins with each of us. Make your mark and say 'I was here.' " Also including footage of people across the world, the message closes out with the track playing and the diva saying, "One day, one message, 1 billion taking action for each other. I'll see you then."

The World Humanitarian Day website launched this week allows folks to post the "individual acts of good" they have done in their communities. By the day of the event, they hope to reach 1 billion people with a single message. Communities will do their part through commemorations and public events.

"We all see the headlines, and we think, 'What can I really do to help?' " Beyoncé said in a statement. "World Humanitarian Day is an opportunity for all of us to work together to make a difference. This is our time to leave our mark on the world and show that we were here and we care."