Meanwhile, Harwood is now keen to speak to former U's striker Dion Dublin about the possibility of replacing Renard.
Dublin, now 35, spent four successful seasons at the Abbey Stadium between 1988 and 1992 before joining Manchester United for £1m - which remains Cambridge's record sale.
He is currently playing in central defence for Championship side Leicester City, but may be keen to leave after new boss Craig Levein made it clear he was no longer a first-choice forward at the Walkers Stadium.
Harwood continued: "If Dion is interested, we would certainly be interested in hearing from him.
"Dion had a memorable time here, and I would certainly not rule out holding an interview with him to see what he has got to say.
"His appointment would certainly be popular and he would also add valuable experience - and possibly get us a few goals while he is at it.
"At the moment though, I am just terribly deflated at the situation because Herve was one of the best people I have ever worked with in football and he will remain a good friend of mine."