Taylor Swift performed a duet with Cher Lloyd during her concert at the Los Angeles Staples Centre on Monday night (19.08.13).

The 'Trouble' singer surprised fans by bringing out the 20-year-old pop star during her sold out performance at the 18,000 capacity venue.

Cher teamed up with Taylor to perform her 2012 hit 'Want U Back' which charted at number 12 in the US Billboard charts.

Taylor described the impromptu collaboration as her ''favourite'' moment of the gig.

The 23-year-old musician wrote: ''One of my favorite moments of the night was @CherLloyd coming out to sing 'Want U Back'. The crowd went insane!! And she's such a fun girl! To everyone who came to the show tonight in LA, I adore you. To anyone coming to the next 3 shows, expect more of the unexpected :) (sic)''

Cher - who has enjoyed mainstream success since initially finding fame on 'The X Factor' UK in 2010 - was clearly thrilled to perform with the pop sensation.

Cher posted a photo of the pair hugging and smiling together backstage with the accompanying caption: ''Had the most amazing time performing with @taylorswift13 ,She's the sweetest girl I've ever met!!! Loved it!!! Xxx (sic)''

Taylor will play her fourth sold-out show at the Staples Centre on Saturday (24.08.13) after which she'll claim the record for the solo artist with the most sell outs gigs at the Los Angeles venue, with 11 to date.

The star will be tied with Latin pop group Mana for the most overall sell outs, for which she's being acknowledged on Tuesday (20.08.13) by Staples Senior Vice President and General Manager Lee Zeidman and officials from 'Red Tour' promoter the Messina Group.