Australian PFA chief Brendan Schwab has warned Sydney FC that Alex Brosque will take the unprecedented step of going to arbitration in a bid to quit the A-League side.
Brosque is desperate to end his five-year spell with the club to take up a deal with Japanese outfit Shimizu S-Pulse believed to be worth around $1.5 million.
Sydney are refusing to allow the striker to leave, claiming a clause in his contract that states he can be transferred should an overseas team make an offer for him, is no longer valid after he signed a new deal at the start of this season.
The A-League champions' vice-chairman Scott Barlow accused Shimizu of breaching FIFA regulations on Tuesday, and said the J-League side held discussions with Brosque in Sydney several months ago.
"A-League clubs have rights in these situations and we will not stand by and let foreign clubs disregard FIFA regulations when approaching our players," Barlow said.
However, Brosque and the Professional Footballers' Australia claim his new deal does not start until April 1, and the Socceroos striker is still playing under his old terms and should be allowed to leave.
"We would like to try and reach and agreement with Sydney for Alex's transfer," Schwab told AAP.
"We do think he is entitled to leave under the terms of his agreement and that is what we are working towards.
"If we can't reach an agreement ... then the next step is independent arbitration which we would refer to."
Under the players' current CBA with Football Federation Australia (FFA), an arbiter has to be provided to rule on any disagreement.
Schwab said Brosque would be the first player in Australia to take his case to arbitration if Sydney refuse to agree to a transfer at a meeting on Thursday.
"There have obviously been lots of cases over the years that have been arbitrated on over a variety of issues, but in terms of the interpretation of a clause, it would be the first of that nature in my experience," Schwab said.
Schwab said Barlow's claims were "unhelpful" but was confident the move can be salvaged and Brosque can link up with the Shizuoka-based side, who finished sixth in the J-League last season.
"Sydney FC have made two rather strong public statements which we deem to be unhelpful, but we can't be responsible for the way Sydney conducts itself," he said.
"We have advised Alex as to his legal rights and hope to reach a resolution with Sydney which would bring about his transfer in accordance to his rights."
A Sydney FC spokesman said the club stand by their ruling but would not make any further comment until after Thursday's meeting.