US President Barack Obama saluted Betty White in a televised birthday tribute, but requested the iconic actress' long-form birth certificate to prove she is, in fact, now 90 years old.

"Dear Betty, You look so fantastic and full of energy, I can't believe you're 90 years old," Mr Obama said during a television special that aired yesterday honouring the actress.

"In fact, I don't believe it. That's why I'm writing to ask if you will be willing to produce a copy of your long-form birth certificate," he continues as he is shown writing at his Oval Office desk. "Thanks and happy birthday, no matter how old you are."

After finishing the note, Mr Obama places a framed photo of White on the table behind his desk. He then plugs in a pair of earbuds and nods his head as the The Golden Girls theme song begins to play.

Mr Obama is also celebrating another important birthday today. His wife, Michelle, turns 48 on the same day White turns 90.

"Betty White's 90th Birthday: A Tribute to America's Golden Girl" aired last night on NBC. Roughly 13.9 million people tuned in for the special, according to The Hollywood Reporter.