Sir Elton John's promoter says the superstar almost collapsed on stage at Auckland's Mt Smart Stadium last night.
The distraught 72-year-old left the stage in tears stage midway through the performance as his voice deserted him.
Medical staff rushed to give John, suffering from walking pneumonia, oxygen on stage as he told them he felt dizzy.
John told the crowd early in the concert he had been diagnosed with "walking pneumonia" on Sunday morning. His voice was "shot", he said, but he was determined to lay on a great show.
"I don't know how much longer I can sing," he told the crowd. "I'll try, but I've got nothing left."
He sang 16 songs of a 25-strong playlist.
His promoter, Michael Chugg, told Newstalk ZB's Heather Du Plessis-Allan the superstar's next two Auckland concerts, which have been moved to Wednesday and Thursday to allow another day of rest, were "definitely going ahead".
But those attending last night's performance won't get a refund for the shortened performance.
"He played over two hours last night, so there's no refunds for last night," Chugg said.
A new statement, issued about 4pm, said the second gig would be delayed until Wednesday, so John has an extra day of recovery on his current medication.
"I'm looking forward to seeing you on Wednesday and Thursday evenings at Mt Smart Stadium," he told his fans.
All Tuesday tickets remain valid for Wednesday. All concert details, including transport, remain the same.
The latest statement said Tuesday ticket holders unable to attend on Wednesday should contact Ticketmaster to request a refund. Limited tickets are still available for Thursday's show.
Air New Zealand said it has introduced special fare flexibility to those affected by the rescheduling.
"As a gesture of goodwill, Air New Zealand is offering customers affected by this change the opportunity to defer travel plans by one day without cost by calling its contact centre," Air New Zealand said in a statement.
"The airline will waive any service fees or fare difference associated with moving the booking."
Passengers who no longer want to travel can choose to the hold the value of their fare in credit for up to 12 months. Service fees will be waived but any fare difference will apply.
John, who had earlier needed medical assistance while on stage, broke down in tears and needed to be assisted from the stage after attempting to launch into Daniel.
Last night, Daniel was No 16 in a 25-strong playlist. Herald concert reviewer Karl Puschmann said John's voice remained powerful during his early songs - until he spoke.
Walking pneumonia is an infection caused by bacteria that primarily affects an individual's lower and upper respiratory tract.
The condition is not as severe as the other forms of pneumonia and in most cases hospitalisation and bed rest are not required for recovery. It goes unnoticed and feels similar to the common cold for most individuals.
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• Elton John cancels Mt Smart Auckland concert mid-performance, loses voice with pneumonia
But fans have continued to praise John's work ethic on social media, thanking him for giving the performance all he had.
"Sir Elton John, what a great concert," wrote one. "Very sad to see you leave but the concert was amazing, you did the best you could."
John later reached out to fans, thanking them for their support and saying he was upset that he could not complete the show.
"I played and sang my heart out, until my voice could sing no more. I'm disappointed, deeply upset and sorry. I gave it all I had. Thank you so much for your extraordinary support and all the love you showed me during tonight's performance. I am eternally grateful."