Legendary crooner Tony Bennett has revealed that he is battling Alzheimer's disease.

In an in-depth profile piece for AARP Magazine, it was revealed that the 94-year-old - known for signature hit 'I Left My Heart In San Francisco' - was diagnosed with the condition in 2016 but has continued to perform and record new music since.

Bennett's wife Susan told the magazine that he has so far not suffered some of the worst side-effects of Alzheimer's - including disorientation and mood swings - although he increasingly struggles with his memory.

"I have my moments and it gets very difficult," she said. "It's no fun arguing with someone who doesn't understand you.

"But I feel badly talking about it because we are so much more fortunate than so many people with this diagnosis. We have such a good team."

Susan went on to reveal that Bennett remains content despite his condition, adding: "He would ask me, 'What is Alzheimer's?' I would explain, but he wouldn't get it. He'd tell me, 'Susan, I feel fine.'

"That's all he could process - that physically he felt great. So, nothing changed in his life. Anything that did change, he wasn't aware of."

Bennett will release a second duet album with Lady Gaga - recorded sporadically between 2018 and early 2020 - this spring.