The Scotland international's first month on loan at Home Park is set to end after Saturday's match at leaders Bristol City.
Argyle boss Paul Sturrock confirmed: "We've chatted to Sunderland and we are just waiting on word back.
"He has done okay for us and he would be a benefit but it is purely in Sunderland's hands at this minute.
"We have been in discussions and we will wait and see what transpires.
"His performances have been consistent. He has been a steady Eddie for us and never let us down."