NEW YORK (AP) — The United Nations has named Leonardo DiCaprio a UN Messenger of Peace with a special focus on climate change.

UN Secretary-General Ban Ki-moon made the announcement Tuesday, calling DiCaprio "a credible voice in the environmental movement." He also invited the actor to the upcoming UN Climate Summit planned for September 23.

DiCaprio said he was honored by the role and that he feels "a moral obligation to speak out at this key moment in human history" about the threat of climate change.

Messengers of Peace are selected from the arts, music, literature and sports. They agree to help bring attention to UN work. Previous actors named to the honor include George Clooney, Edward Norton and Charlize Theron.

The 39-year-old "Wolf of Wall Street" star founded an environmental foundation in 1998.