The Manchester City stopper has come under pressure ahead of England's vital World Cup qualifiers with Montenegro and Poland following a string of errors in high-profile matches.
Hart remains first choice as England goalkeeper, but Celtic's Fraser Forster and Norwich counterpart John Ruddy are hoping to replace the 26-year-old in the national team.
Forster, a former Newcastle team-mate of Harper, has been in excellent form since moving to Celtic - impressing particularly in the Champions League in the past two seasons.
"I think it's fantastic man-management to stand by Joe. He is England's number one - rightly so as well, I don't think he's ever let us down," Harper said during an interview at St James' Park.
"We've two huge games coming up where you need that experience. He does have Fraser Forster breathing down his neck.
"I know Fraser obviously very well from his time here, and John Ruddy as well, but I think we've tried the experimental one of putting goalkeepers in in big games in the past and it didn't quite work out
"So it's very much a case of sticking with Joe. He's just had a difficult spell. We all have them. We all make mistakes.
"But he's a top-drawer goalkeeper who is mentally very, very strong, and hopefully he can see us through to the World Cup next year."