Jessica and Ashlee Simpson to perform duet

Jessica and Ashlee Simpson are set to duet together.

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The sisters – who have each forged their own successful solo careers — have been writing songs together for years and are now considering teaming up in the recording studio.

Ashlee told E! Online: “We write well together. I can’t say never, but she’s definitely got her own style, and I have my own style. But who knows?”

The Pieces of Me singer also lent her support to troubled singer Britney Spears, who has faced a barrage of criticism following her disastrous performance at the MTV Video Music Awards earlier this month.

Ashlee — who was caught miming on her ‘live’ performance on Saturday Night Live in 2004 — said: “To tell you the truth, I have not seen the performance. I was actually sitting upstairs, so I can’t say anything on it–but I wish her the best.

“I think we all have our ups and our downs, and you have got to look for the positive side of things.”

Ashlee and boyfriend Pete Wentz are reportedly engaged. The Fall Out Boy rocker is said to have proposed after his Live Earth performance in New Jersey in July.