Barcelona can not buy more Liverpool players by 2020, unless they are willing to pay a £ 90m ($ 158m) premium, unlike any transfer.
The clause was agreed by Liverpool Sports Director Michael Edwards during the transfer of Philip Coutinho to the Nou Camp of 142 million pounds ($ 249 million) in November's Camp Nou.
It is an attempt to prevent the Spanish giants from catching even more talent in Jürgen Klop in the near future.
The news should calm the reports in Spain, which indicated that Barcelona is interested in a move for Sadio Mane, who is currently involved in talks on a better deal at Enfield.
Clop said: "It's a good sign for the club, it's an improved situation that these players do not use and then we go. It's nice … sign the contracts, but now, go again. "
Many Liverpool officials remained frustrated by Barcelona's strides at Coutinho, with the 26-year-old missing game at the start of last season, saying it had bad backs.
Coutinho was subject to three unsuccessful bouts from Barcelona last summer, of which the largest was worth 113 million pounds ($ 198 million) and handed him a transfer request in an attempt to force a move.
It was unsuccessful, but the two clubs reached a deal in January, and the Brazilian signed an agreement in Catalonia by the summer of 2023.
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