United Kingdom, March 13 -- Billy Joel is "totally healthy", Christie Brinkley's daughter has insisted.

The 75-year-old singer recently announced he was postponing his tour by several months for medical reasons but Sailor Brinkley-Cook - who is the offspring of the 'Uptown Girl' hitmaker's second wife and her now ex-husband Peter Cook - has reassured fans he is "doing great" and will be back on stage as soon as he can.

The 26-year-old beauty - who calls the musician "Uncle Billy" - told Us Weekly magazine: "He's doing great. He's totally healthy and it's just some things that he has to deal with."

Sailor admitted Billy is "really upset" at having to delay the concerts.

She added: "I'm excited for him to be able to get back."

The 'Pia...