The agent of Henrikh Mkhitaryan said it would be wrong to abandon attempts to get the Borussia Dortmund midfielder a move to Manchester United, the BBC reports.
The Bundesliga club are refusing to let the 27-year-old leave following the departures of both Mats Hummels and Ilkay Gundongan this summer.
“It would be a sin to stop talking,” said agent Mino Raiola.
“I am a positive guy. If I wasn’t confident of reaching some kind of conclusion, I wouldn’t try.”
The Armenian has a year left on his contract and has told Dortmund he will not sign another deal, with United his preferred option.
Raiola added: “I am very proud Manchester United want him and the talks are being held in a good atmosphere, but at the moment Dortmund are still saying no.”
New United manager Jose Mourinho is attempting to improve his squad after replacing Louis van Gaal.
“Manchester United is a great club, with a great coach,” said Raiola.