South African scrum-half Ruan Pienaar is to leave Ulster at the end of the season when his contract runs out.
Pienaar, 32, signed a new deal with the Irish province in 2013 after turning down the chance to join then European champions Toulon.
The Springbok joined Ulster in 2010 and has racked up 777 points in 118 competitive games over six seasons.
Pienaar, capped 88 times, is understood to be attracting interest from French Top 14 side Montpellier.
A statement released by Ulster Rugby on Wednesday morning indicated that both "the club and the player were very keen to extend his stay in Belfast" but that did not prove possible.
"Operations director Bryn Cunningham and director of rugby Les Kiss have been working with the IRFU over the past six months to reach a desirable outcome. Unfortunately, a contract extension was not possible due to the IRFU's succession policy," read the statement.
In response, the Irish Rugby Football Union's Performance Director David Nucifora said that the IRFU had "informed Ulster Rugby during the 2015-16 season that it would not sanction a further extension" of Pienaar's contract.
"The IRFU recognises the contribution that Ruan Pienaar has made to Ulster Rugby over the seven year period he will have been with the club,
"It is vital for both Ulster and Irish rugby that the province develop indigenous talent in this position and an extension of Ruan's contract would further prevent Irish qualified Ulster players from maximising their developmental potential and becoming stars for both Ulster and Ireland."
Pienaar, who was a member of the Ulster squad which reached the Heineken Cup final in 2012, was keen to point out that he was "not moving on for a new adventure or for financial reasons".
Ulster 'did everything it could to keep me'
He said: "I wanted to stay and I know that Ulster Rugby did everything it could to keep me in Belfast. Ulster is special to me and my family now.
"The club has given me a lot and I'd like to be in a position to give something back in the future if possible."
"It is sad that this will be my last season as an Ulster player but I will be doing everything to ensure that we make it a successful campaign."
Director of rugby Kiss praised Ruan's contribution to the club.
"Ruan has been an outstanding servant to Ulster Rugby over the past six years and he will be a huge loss for us next season," he said.
"For me, he is a fantastic player, but he is an even better person, who is much-loved by his team-mates, the staff and management, and the wider rugby community here in Ulster.
"His influence within the squad, both on and off the field, is truly remarkable, whether that is through match-winning contributions, or mentoring the promising players coming through our pathway.
"Indeed, he has played a big part in helping us to develop a large group of talented young backline players who have gone on to represent Ireland in recent years.
"He is a consummate professional and I have absolutely no doubt that he will give everything to the Ulster cause for the rest of the season. Our hope is that he will one day return to the province to continue to have a positive impact on rugby in Ulster."