The Magpies boss highlighted the club’s lack of major signings over the past three transfer windows and was directly questioned on whether securing Isak’s future is crucial.
With Newcastle pushing for another Champions League spot, keeping their star striker remains a top priority.
Howe said: "Linked to a number of other players really, I think we have to try and keep our best players.
“I think that’s crucial to our short-term success and our long-term success, so sitting here as the manager of the football club, I’d be saying we need to keep the group together, and we need to add the other way.
"We haven't added (to the first team) in a long time in various transfer windows, for the reasons we've all discussed. But we need to move the team forward and we can't lose our best players."