LOS ANGELES — A conflict in negotiations among multiple parties, notably MLB, the Players Association, Nippon Professional Baseball (NPB) and Shohei Otani’s current team imperils the much-anticipated arrival this winter of Japan’s best player, The Post has learned.

The MLB-NPB posting agreement expired Tuesday. The sides, though, were close to an agreement to move to a system whereby the Japanese team losing a player to MLB would receive a percentage of the deal the player signed with an MLB club — believed to be between 15 and 20 percent.

However, Otani’s team, the Nippon Ham Fighters, refused to give its needed vote to the deal unless the righty pitcher was grandfathered into the old deal, whereby the Fighters would receive the maximum $20 million in exchange for posting him prior to his Japanese free agency.

The collective bargaining agreement agreed to last offseason made foreign players 25 and older who want to play in the majors unfettered free agents. Those under 25 — like the 23-year-old Otani — are subject to the international pool caps, so the righty thrower is not all that different from, say, a 16-year-old from the Dominican. Thus, he is likely to receive between $300,000 and about $3.5 million, and 20 percent of that would be a pittance for the Fighters.

MLB is willing to make an exception for Otani and let him come under the old system.

But MLB cannot enter into any transfer agreement with any country — Japan, Korea, Cuba, Mexico, etc. — without approval from the MLB Players Association, as stated in the CBA. And the union, to date, has refused to make an exception for Otani, concerned about the precedent and fairness of the player receiving, say, $300,000 and his former team $20 million.

The union has tried to deal with Otani and his camp directly, but as of Wednesday had been unsuccessful.

Unless all these parties reach common ground, no treaty will be in place to allow Otani to come to MLB despite his desires.

Otani, the best pitcher and perhaps also the best hitter in Japan, will not even fall under the union umbrella immediately because he would be signing a minor league deal as an under-25 player subject to the international pools.

The union believes the mechanism to get Otani to the majors would move much quicker if he picked an agent certified by the association.

Because he will sign a minor league deal and not immediately be on a 40-man roster, Otani does not have to select a certified agent, but he has been sorting through possibilities and the expectation is he will pick someone. The strongest industry buzz is Scott Boras is the front-runner, but at the World Series this week, Boras said he has not been officially notified that he was selected.

Otani has been using a Japanese lawyer with whom he was familiar to work through the process for now.

If Otani were to wait two years and stay healthy and desirable, he would be 25 and able to sign a contract for $200 million or more. But Otani seems unconcerned with those riches and wants to come to MLB as soon as possible.

In general, the new agreement would be favorable to the union because it will limit the amount of money sent to Japanese teams and, theoretically, that means more for the players. It was not long ago that there was a blind bidding process and only the high bid got exclusive rights to negotiate with a Japanese player.

In the case of Daisuke Matsuzaka and Yu Darvish, that meant more than $51 million for the Japanese teams, but then that limited how much the players received in their contracts — Matsuzaka got a five-year, $50 million deal and Darvish six years at $56 million.

The rule was changed in the now-expired agreement whereby any teams that had the high bid to negotiate could and that bid was capped at $20 million. Under those rules, the Yankees gave Masahiro Tanaka a seven-year, $155 million contract.

MLB is trying to establish an across-the-board posting system that will cover all foreign leagues, notably Cuba, to try to — among other things — have a formal agreement with that country to avoid the need for players to dangerously defect and/or have to pay large sums of future earnings to third parties to do so.