Both players come off contract in June.
Howe was asked about the futures of both locals - less than an hour after a new deal for Fabian Schar had signed an extension at St James' Park.
Reflecting on Longstaff, he said: "We've been talking with him and representatives for a while and we hope that we can reach a successful conclusion there.
"With Paul Dummett, we're keen for him to stay. Fingers crossed we can find a positive resolution."
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