The Spanish giants can only sign one of the Reds’ stars if they pay an extra £89m (€100m) on top of any transfer fee until 2020.
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It has emerged Liverpool inserted the clause when they sanctioned the £142m sale of Philippe Coutinho to Barcelona in January.
That means it could cost Barcelona over £200m if they were to swoop for the likes of Salah or Van Dijk.
Sadio Mane has also been linked with a move to Spain but it appears none of Coutinho’s former team-mates will be following him to the Nou Camp any time soon.
Barcelona previously signed Luis Suarez from the Merseysiders in a controversial deal in 2014.
The Uruguay international effectively forced his move to the Nou Camp despite the Reds being desperate to keep him.
Liverpool also reluctantly allowed Brazil ace Coutinho leave for Spain but were angered by the La Liga side’s pursuit.
The previous summer they warned Barcelona not to make any more approaches for him or they would be reported to FIFA.
Barca tried and failed to launch a move before deadline day, with Coutinho not playing for the Reds that season until the transfer window had closed.
But in January, Liverpool manager Jurgen Klopp granted Coutinho’s wish to move to the Catalan side only if the club’s terms were met.
Liverpool sporting director Michael Edwards negotiated a clause that stops Barcelona returning for any more of their best players in the next two years.
The La Liga champions would have to pay an extra £89m on top of any transfer fee if they did try to lure a Liverpool star away.
Barcelona agreed to the bizarre clause which shows their desperation to bring Coutinho to the Nou Camp earlier this year.
And it has now emerged they were initially agitated by Edwards’ insistence on the clause being inserted but were forced to agree to it if they wanted Coutinho.
Since his arrival at the Nou Camp Coutinho has blown hot and cold.
The Brazilian has scored just five goals all season for Barca and has not proven the replacement for Neymar that many fans were hoping he would turn out to be.
Instead, the playmaker has increasingly played servant to the likes of Suarez and Lionel Messi, assisting them with their goal tallies.
Barca sit top of La Liga, a point ahead of Sevilla after 12 games and four points in front of rivals Real Madrid.