Warren Gatland has revealed the Welsh national team's working relationship with the Ospreys is his "most disappointing thing" as Wales coach.
The Ospreys, Wales' most successful region, currently have eight players in coach Gatland's Wales squad to face the Barbarians in Cardiff on Saturday.
Gatland wants Wales and the Ospreys to stop "banging our heads against each other and making life difficult".
But Ospreys chief Roger Blyth thinks the bond with Wales is "pretty strong".
Gatland will go head-to-head with Ospreys director of coaching Scott Johnson on Saturday as the Liberty Stadium boss is the Barbarians' backs coach in their international with Wales at the Millennium Stadium.
Three-time Magners League winners the Ospreys and Gatland are understood to have differing opinions on style of play, player preparation for Welsh internationals and top-up fees for keeping Wales' top stars in Wales.
New Zealander Gatland says he and the Ospreys management, which includes former Wales coach Johnson and the Welsh Rugby Union's one-time fitness and conditioning coach Andrew Hore, should be "working together" for the good of Welsh rugby.
"It is the most disappointing thing since I've been at Wales, you'd like to think that us and the Ospreys should have a really, really close relationship," Gatland told BBC Wales' Scrum V show.
"And be working together, helping each other out and assisting each other at every opportunity.
"The unfortunate thing is, it just hasn't bonded or blended in any way that I would've like it.
"The relationship with the Blues has been great and the Dragons and Scarlets, but for whatever reason, and I don't know what it is, we just haven't clicked with the Ospreys.
"I'm telling them the door is open. I believe we should have a much closer relationship than we do - and not always be at each other and banging our heads against each other and making life difficult.
"Ideally you would like a close working relationship going forward and perhaps with the changes in roles at the Ospreys and maybe a few players leaving that we will be able to do that in the future."
However, the Ospreys' joint managing director Blyth dismisses Gatland's claims of a poor relationship between the Welsh Rugby Union and this season's Magners League play-off semi-finalists.
"I'm rather dumbfounded by Warren's comments," Blyth told Scrum V.
"I've always thought we had a pretty strong relationship with the union. The contribution we have made over the years has been second to none, so his comments are rather mystifying.
"We get regular visits from his national coaches. Robin McBryde is down a lot of the time and certainly Neil Jenkins etc.
"I have got to say Warren hasn't been with us that much, I think he has only been with us two or three times since Scott Johnson has been our coach."
The Ospreys boast Wales stars such as Alun Wyn Jones, Shane Williams, Ryan Jones, Adam Jones and Paul James.
And asked if it is a hindrance that the Ospreys have so many Wales players, Gatland replied: "Yes, it has been in the past.
"In my first game there were 13 Ospreys that started and that number has slowly dwindled down.
"There might only be six Ospreys that go to the World Cup.
"From a selection point of a view as an international coach, you don't want all of the talent being in one area, ideally you want it spread around."