0646 GMT January 16, 2022
The weekly meeting, which is to be chaired by Prime Minister Pedro Sanchez, is scheduled to convene in the Catalan capital Barcelona on Friday.
"[Sanchez's government]...will want to provoke us, they will be angry, they would like us to be violent, and they will not succeed," the prisoners wrote, Presstv Reported.
"Our strength also lies in maintaining, always and everywhere, a civic and peaceful attitude," they added.
Hundreds of national police will be deployed in Barcelona amid fears of re-surging violence.
Also on Thursday, four of the signatories - Jordi Turull, Josep Rull, Jordi Sanchez and Joaquim Forn - unexpectedly called off a hunger strike they had begun at the start of December.
Last year, the northeastern rich region unilaterally declared independence following a referendum, violating the country’s constitution that forbids secession and prompting violent clashes between Catalans and the police.
Batons flew and the law enforcement deployed rubber bullets during the standoff that caught much international attention.
An unexpected meeting is also to follow between Sanchez and pro-independence regional leader Quim Torra as another bid to ease tensions.