The 26-year-old Brazil midfielder has been linked with a series of potential suitors, including Manchester City, Arsenal and Paris Saint-Germain after a hugely impressive spell on Tyneside.
Guimaraes is understood to have a £100 million release clause in his existing contract, which is due to run until 2028, but a report this week suggested that clause will be in force only from the last week of May until the beginning of the final week in June.
Howe, speaking ahead of Saturday's clash with bottom club Sheffield United, said he did not "tend to worry" over issues outside his control. "It goes without saying what my thoughts on the Bruno situation are," he said. "We want to keep him, we want to build our team around him and he's an integral part of what we are doing.
"His form has been very good, he seems very happy and settled, he will be thinking about a busy summer ahead and where we can hopefully take the team. He is a big part of that. We are not in control of that, so we shall see."
Asked specifically about the clause, Howe did not go into detail but said: "Having that was well planned and structured by the club, in a sense that there is a finish point. We don't want the constant speculation, I don't think that's healthy for the player or for us."
Guimaraes, who joined Newcastle in January 2022, and Sweden striker Alexander Isak are being closely monitored by other clubs, with Newcastle reportedly fearing they may have to sell one of their big names in the summer transfer window to satisfy Premier League financial rules.
Howe has repeatedly expressed his intention to retain his top players but is acutely aware of the need to balance the books after a £400 million recruitment drive under the club's Saudi-backed owners.
Aske
Read on besoccer.com