# Problems whose decidability status is unknown but known to be less hard than the halting problem

Are there problems the decidability of which is unknown but it is known for certain that the problems are less hard than the halting problem.

• – Kaveh Jan 4 '16 at 7:38

Assuming that by "less hard" you mean "reducible to", then any problem that is known to be in $RE$ but not known to be in $R$ satisfies this condition.