  A ring is SSP if the sum of two direct summands is a direct summand. A ring
has internal cancellation if every its (von Neumann) regular elements are
unit-regular. We show that in an SSP ring having internal cancellation, any
regular element is special clean. Our main results also imply that for any SSP
ring internal cancellation and idempotent stable range $1$ coincide with each
other. Internal cancellation over SSP was then characterized by special clean
elements.
