Britney Spears is close to signing a deal to appear on the US 'X Factor'.

The 'Toxic' singer is said to be in the ''final stretch'' of negotiations with reality TV mogul Simon Cowell to become a judge on the singing show.

Deadline.com added the final pay deal with see Britney earn ''probably closer to $15 million'' for the series, after it was previously reported she turned down a $10 million offer.

The star's pay will exceed the $12 million which Jennifer Lopez makes from starring in rival series 'American Idol'.

Simon is looking for two judges to replace Nicole Scherzinger and Paula Abdul, who were axed after the first series of 'The X Factor' after ratings didn't meet expectations. He and music executive L.A. Reid will stay on the panel.

One of the sticking points in negotiations between Britney and Simon was reportedly the number of series she would have to commit to.

A source told HollywoodLife.com: ''Money is not an issue for the show. As of now, they are looking to pay her $12-15 million for the first season, with a drastic price hike for a second year based on ratings performance.

''Simon Cowell wants at least a two-year commitment and Britney wants an out clause if she doesn't want to continue after one year of service.''

Simon has been particularly complimentary about the star in recent weeks, praising Britney - who has sons Sean Preston, six, and Jayden James, five, with ex-husband Kevin Federline - for her ''resilience'' in juggling her music and family life.

He said: ''I'm fascinated by her. The fact that she's one of the most talked about - not just pop stars - but people in the world today, means that you've got this star power.

''This girl has got resilience. I would think that if she's managed to sustain a family, a career, which is tough, ['X Factor' would be] a walk in the park.''