Adele won't cheer on England in the World Cup because she wants to protect her voice.

The 'Someone Like You' hitmaker has made "quite the sacrifice" to ensure she's at her best for her Las Vegas residency as she's usually a vocal fan of her home country's soccer side, but has been watching their games on TV in near-silence.

A source told The Sun on Sunday newspaper's Bizarre column: “Adele has been keen to avoid excessive stress on her vocal cords.

"She is really committing to giving her best each night at her show.

“One of the key features has been protecting her voice in between the Friday and Saturday nights.

"She wants it in top shape for each show and is going to extreme lengths.

“So before shows she rarely speaks to anyone, and if she does, then it’s a whisper.

"People know she is not being rude, but looking after herself. It is about staying healthy and strong.

“Usually she’d be screaming and shouting in support of the boys, but she is holding it in for the sake of her cords.

"It’s quite a sacrifice.”

It was recently claimed The Colosseum at Caesars Palace had installed a "complex" system to guarantee the "best possible" air quality in the venue in a bid to help 34-year-old Adele - who underwent vocal cord surgery in 2011 - protect her voice.

A source said: "They’ve had complex systems installed before, but this one really is on another level. The system works by combining dehumidifiers, purification units, water molecule dispersal and cooling fans in the preparation room and then guiding that air around the stage when she performs. Adele is getting the best possible air to protect her voice."