The goalkeeper last played for the club just over a year ago.
And Benitez yesterday revealed that the 32-year-old, under contract at St James’s Park until 2020, is available in next month’s transfer window.
Asked if he had spoken to Elliot about his situation, United’s manager said: “Yes, he knows.
“The way modern football is now, sometimes you can’t talk to your player. I had a surprise years ago when I was talking to a player, and he said ‘no, don’t talk to me, talk with my agent’, but I was talking with Rob.
“He’s not playing and he’s available, and that’s it. We have four keepers, and we can cannot keep (him).”
Elliot could opt to see out his contract at the club, though Benitez believes the Republic of Ireland international knows he must play this and next season.
“There’s a point where you can say ‘I’m fine here’, but there’s also a point where you say ‘hmmm, if I don’t play now, what will happen next?,” said Benitez. “So I think he’s keen to play.”