P!nk National Anthem Performance in Jeopardy ... This Flu's No Joke!!!

2/3/2018 1:07 PM PST

P!nk's Super Bowl National Anthem Performance in Jeopardy Due to Flu

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P!nk's got the flu -- the nasty flu that's been spreading and intensifying this season -- and her illness could keep her from singing "The Star-Spangled Banner" on Super Bowl Sunday.

Sources close to Super Bowl LII production tell TMZ ... P!nk had a really tough time making it through her rehearsal Thursday night. We're told it didn't go smoothly ... and everyone involved didn't feel good when it was over.

There's more cause for concern too -- P!nk managed to power through her pre-Super Bowl concert Friday at The Armory in Minneapolis ... but had to rely to backup singers and the audience often to sing for her.

She even had to cut off her track "Beautiful Trauma" shortly after starting, telling the crowd, "I can't do it. I hate this ... I can't do that song. I'm sorry."

Trying to practice the flu away. I’ve been waiting to sing this song since 1991 when I saw my idol, Whitney Houston, own this song. And now, my chance has finally come. And it just so happens that this chance comes when I have two small Petri dish kids who literally cough INTO MY MOUTH and rub their snot on my cheek. You can’t write this stuff I swear! And here we are. I’ve arrived at another one of my dreams which is slowly becoming a sort of nightmare. I will tell you, this is one of the biggest honors of my life, singing this song in front of my family, my military family, my dad and brother and step mama and family and the world. And the EAGLES!?!?! I promise I will do my best, as I always do. As far as the gremlins that got me into this mess, you can cough at me for the rest of your lives. If it’s a contest, babies, you win. #spreadthelove #spreadthegerms #pleasegivememyvoiceback #ificansingimgonnakillit

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The singer assured fans she's trying to fight through her illness and "practice the flu away," but as we know ... the flu's hit hard this year and takes a few days to recover ... even with rest. And it doesn't seem like P!nk's resting too much.

Still, she says she promises she's going to do her best.

We've reached out to reps for SB52 to see what the backup plan is if P!nk can't sing the National Anthem ... so far, no word back.