The United Nations secretary-general marked the International Day of Persons with Disabilities by welcoming music star Stevie Wonder as the organization's newest Messenger of Peace.  But amidst the festivities, the message was clear - about 10 percent of the world's population suffers from some type of disability and they often encounter many disadvantages.

 U.N. chief Ban Ki-moon said disabilities affect the lives of people everywhere.

"An estimated one person in four around the world is affected by disability, which can touch any of us at any time in our lives," he said.

Mr. Ban said physical, mental or sensory impairments affect not only the people who have them, but also their caregivers and families.

The secretary-general warned that people with disabilities encounter many disadvantages and often are among the poorest and most excluded members of society.  But when they are empowered, it changes their lives dramatically.

He welcomed U.S. singer Stevie Wonder, who has been blind since birth, as the U.N.'s new Messenger of Peace for Persons with Disabilities.

"We all know Stevie Wonder is a musical genius whose songs have given pleasure and hope to millions of people around the world.  He is also a great humanitarian who has campaigned against apartheid, for children in need and for persons with disabilities," he said.

The singer told a press conference that he hopes those without disabilities will show they care for those with them, by opening all the doors and possibilities for them.

"I hope that you would all have the vision to open up the vision - in not only your eyes, but [also] in your mind and spirit - in seeing that a person who is left without an opportunity - one person - means that we all are with a disability," said Wonder.  "And that disability is a lack of being able to care.  So I would hope that every single human being and every single world leader will commit themselves to making this world a better place and accessible for every single human being on this planet," he said.

Wonder said he would use his celebrity to speak out - and sing - on the subject.  He said he would like to raise awareness of new technologies that can help improve the lives of people with specific disabilities and work to make them more accessible and affordable for them.

Before departing U.N. headquarters, Wonder was serenaded by a group of New York school children with one of his most recognizable tunes.  He then sang a bit of it for them.