The sport of rugby league on Tuesday joined swimming by banning transgender players from international competition, as World Athletics said it was also considering a rule change.
Rugby league authorities said transgender athletes would be "unable to play" in international matches while they undertook consultations and research to finalise a new policy for 2023.
They cited the "welfare, legal and reputational risk" to the game and players in taking their decision.
The 13-a-side game's governing body acted a day after international swimming effectively banned transgender athletes from women's races, placing them instead in a new "open category".
World Athletics hinted at tougher policies on transgender athletes taking part in women's events, with its president Sebastian Coe saying fairness is more important than inclusion.
Sports are drawing up new regulations on participation after the International Olympic Committee last year announced guidelines while asking federations to produce their own "sport-specific" rule.
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The issue has ignited into a fractious debate between those fighting for transgender athletes' rights to compete freely as women and those arguing they enjoy an unfair physiological advantage.
The International Rugby League's announcement means transgender athletes will be banned from this year's Women's Rugby League World Cup in England in November.
"The IRL reaffirms its belief that rugby league is a game for all and that anyone and everyone can play our sport," it said in a statement.
But the sport said it had to balance each player's right to take part against the perceived risk to other players "and to ensure all are given a fair hearing".
'In the gutter'
Rugby league's governing body said it would work with the eight nations taking part in the Women's Rugby League World Cup for a "future trans women inclusion policy in 2023", taking into account the "unique characteristics" of rugby league.
Transgender former New South Wales rugby player Caroline Layt criticised the league's decision.
"We are human beings, we have feelings, and we feel like we are being singled out," Layt told AFP.
"Basically what they're saying is: 'We don't want you.'"
Swimming's governing body FINA made its decision to exclude transgender swimmers from women's races after setting up legal, medical and athletes' committees to examine the issue.
FINA decided that male-to-female transgender athletes could only join women's races if they had not experienced any part of male puberty.
It said its medical committee found that males acquired advantages in puberty, including in the size of their organs and bones, that were not lost in hormone suppression.
World Athletics president Coe hinted Monday that track and field could follow swimming in bringing in a tougher policy on transgender athletes competing in women's events.
"My responsibility is to protect the integrity of women's sport and we take that very seriously, and if it means that we have to make adjustments to protocols going forward, we will," said Coe, who attended the swimming world championships in Budapest on Sunday.
"I've always made it clear: if we ever get pushed into a corner to that point where we're making a judgement about fairness or inclusion, I will always fall down on the side of fairness."
Under World Athletics rules, transgender women have to show they have low testosterone levels for at least 12 months before competition.
Cycling's governing body, the UCI, has also toughened its rules on transgender eligibility by doubling the time period before a rider transitioning from male to female can compete.
The International Olympic Committee, whose executive board meet in Lausanne on Friday, has not stated whether it envisages a third category for Olympic Games.
Instead the IOC told AFP it wants to leave individual federations "to determine the threshold from which an advantage may become disproportionate and to develop the necessary mechanisms to compensate for that".