Will Britney Spears lip sync during Carpool Karaoke?

Britney Spears will appear on James Corden's wildly popular Carpool Karaoke sketch on Thursday in a ramp-up of publicity before she makes her return to the MTV VMA awards ceremony after nine years.

However, a trailer for the sketch released on Wednesday suggests that Spears doesn't actually sing while in the car with the British comedian and presenter.

Corden is seen thanking Spears, an LA resident, for helping him navigate the city's traffic, before he sings along to her 2003 hit Toxic. However, Spears does not join in, but simply mouths the words.

Is Britney Spears looking uncomfortable because she didn't know she had to sing during Carpool Karaoke?

On YouTube, commenters have already re-named the skit "Lipsync karaoke" and slammed the Baby One More Time singer for not singing. Others, however, suggest that the full sketch will involve Spears singing, and this is just a teaser.

On Twitter, people had similar thoughts:

Her performance will remain to be seen when the full clip is released overnight.