Sia has branded her performance at the star-studded wedding of Hollywood actors Jennifer Aniston and Justin Theroux as ‘laughable’.

Speaking in a radio interview on Nova 969’s Fitzy & Wippa show, the Australian songstress admitted her voice cracked during a rendition of one of her many hit songs.

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“I went for the ‘Chandelier’ chorus and it was like, it was actually hilarious,” Sia, 39, said.

“It sounded like three weird squeaky notes at the same time were coming out, it ruined the entire chorus.”

Sia said the stuff-up wasn’t the first time she’s cracked under pressure in front of a high-profile audience member.

She opened up about another performance in front of US President Barack Obama last year, during which she was unable to hit the high notes.

The performance, at the Democratic National Committee’s LGBT Gala, was ‘hilarious’, according to the Adelaide-born singer.

“I think I did three songs and I think the end was ‘Titanium’ and I just couldn’t even hit that high note by the end, it was hilarious,” she told the radio hosts.

“That was for real, I opened my mouth and a squeak came out.”