The 26-year old spent the second half of the last campaign on loan at Hannover, but he is currently set to return to Arsene Wenger's side in time for pre-season, despite interest from Hamburg too.
Djourou still has another two years remaining on his contract at the Emirates Stadium, although Dufner is hopeful of securing his return to Germany.
"We are in touch with Arsenal FC and we feel talks with the clubs have been put on the right track. We are confident. The lad will now need to make a decision," he explained to BILD.
"He needs to say where the road will lead him next. He knows what Hannover 96 is about and we definitely did the best we could. I hope this will be enough to see him decide for us."
Hamburg general manager Oliver Kreuzer had previously boasted that Hamburg would be a better option for Djourou, saying: "HSV is HSV, and we are just a better club," but Dufner was keen to avoid becoming involved in a row.
"We are trying to sign a player. We are not out to belittle a competitor," he said.