Full back Kieran Trippier has been strongly linked with Bayern Munich.
"A few things to say on Kieran's situation. We hope he will stay and we're very confident he will be part of our long-term future," Howe told a press conference ahead of his side's FA Cup fourth-round game at Fulham.
"But I have to make it clear he has never asked to leave or even questioned his future here. We've had conversations in the last week and it's always been about Newcastle.
"His situation is finished. I've been in football long enough to never say 100%. I don't want to look stupid but he's 100% committed."
Howe recently spoke of Newcastle being held back in the transfer market by Financial Fair Play rules, and there has also been speculation around the futures of Miguel Almiron and Callum Wilson.
The manager said he is desperate to keep Almiron and that Wilson was 100% committed to the club, but the same could not be said for Joelinton.
The Brazilian midfielder suffered a serious thigh injury in the last round of the FA Cup against Sunderland which will keep him out of action until May, and the player and club have yet to agree a contract extension.
"Massive blow for us," Howe said. "We knew when he did the injury it immediately didn't look good. We didn't know he'd be out as long.
"It's a possibility (that he's played his last game for the club) but I hope that's not the case… I want him to stay. Before a player signs a contract he has to be happy with everything... and so it's a possibility he'll be sold in the summer."
Newcastle face Fulham on Saturday, a chance to put their poor league form behind them, where they have lost the last four games.
"It is a big moment in our season as the Sunderland game was, this is an important competition for us now, a new dynamic because of what's gone before," Howe said.
"We are desperate to get our best form back and progress."
