MADRID - UN Secretary General Kofi Annan celebrated his 64th birthday with a smile and a song as he opened a world conference -- on aging.

"I turned 64 years old today," said the graying Ghanaian diplomat.

"Will you still need me, Will you still feed me, When I'm 64?" Annan asked, as he urged policymakers from 160 nations to put older people on their policy agenda.

"I trust the answer is 'yes'," he added, to applause and laughter.