The Northern Irishman has worked wonders on Wearside since taking over from Steve Bruce in December, but the Black Cats' impressive form has attracted attention.
However, O'Neill is defiant that the pair will stay put and instead be joined by more talented players at the Stadium of Light.
"The modern game moves so quickly that just about anything can happen. But I'm happy to say the owner agrees with me that we want to keep our very best players at the club because we are looking to build something here and move forward," he told the Sunderland Echo.
"You don't tend to do that if you are selling your best players. We have a squad in a process of development.
"We have a lot of work to do, and I think it is clear that we need to strengthen. We remain very much a club that is looking to go forward."
Sunderland are currently ninth in the Premier League table, just three points behind Liverpool.