Taylor Swift sang with Nelly at Karlie Kloss' birthday party.

Taylor Swift

Taylor Swift

The 26-year-old singer joined the 41-year-old rapper on stage at her best friend's bash in the Hamptons on Saturday (06.08.16) night, where she took on Kelly Rowland's vocals for a rendition of his hit 'Dilemma', much to the delight of the assembled guests, People reports.

This isn't the first time the pair have performed together as last year, Nelly was a guest at Taylor's gig in St. Louis, Missouri, and the two, along with Haim, sang his single 'Hot in Herre'.

Karlie turned 24 on August 3, and Taylor marked the occasion by praising her an an "exquisite person" and an inspiration.

Sharing a selfie of them both, she wrote: "I LOVE YOU KARLIE. You're such an exquisite person, always trying to make things better for others. Every day I'm inspired by how giving, loving, and thoughtful you are. Happy 24th Birthday!!! @karliekloss. (sic)"

And though they couldn't spent the day together, the Bad Blood' hitmaker ensured she was able to chat to her friend via FaceTime.

Karlie shared a picture of her iPad - with Taylor's face visible - alongside a huge bouquet of flowers in a field and wrote: "When you're halfway around the world & your best friend still finds a way to celebrate 24 with you @taylorswift13 (sic)"

Karlie recently credited Taylor and their 'squad' for giving her confidence.

She said: "I grew up being the tallest in my class and was always teased for being skinny. Whether it was because of those people at school or people online now, I had to develop a thick skin.

"You have to learn to cope with people's opinions - it is so important for women to be surrounded by people who truly support them. You have to have a core support group."

Despite accusations the group is elitist, Karlie insists her friends are all very "kind and caring" and she loves the fact they will always try and make time for one another, no matter how busy their schedules are.

She shared: "My friends are kind, caring, thoughtful people. I think that's what draws everyone in the group together. We are all very supportive of each other. We're a big network of really great friends who all have very international schedules and lives. We try to get together as much as possible, even if we're all travelling in different places."

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