NO

Problem:
 U12(tt()) -> s(plus(N,M))
 U11(tt()) -> U12(tt())
 plus(N,0()) -> N
 plus(N,s(M)) -> U11(tt())

Proof:
 Fresh Variable Processor:
  loop length: 1
  terms:
   U12(tt())
  context: s(plus([],M))
  substitution:
   N -> U12(tt())
  Qed