Ireland coach Joe Schmidt has criticised World Rugby for limiting World Cup squads to 31 players, saying it is not in the interests of player welfare.
All sides at the tournament in Japan will play at least four times, with many facing turnarounds of as little as five days between matches.
Ireland begin their World Cup campaign against Scotland on September 22. Six days later they face Japan, before playing Russia just five days after that.
Given the circumstances, Schmidt believes he should be able to include more than 31 players in his squad, saying: "I think it's a very tight number that World Rugby limit you to.
"They talk about player welfare, but we have a six-day turnaround into a five-day turnaround, and 31 players; it's very, very complicated.
"I'm not saying that's just tough for us - all the teams have tight turnarounds at stages."
Ireland beat Italy 29-10 in their first World Cup warm-up match in Dublin on Saturday, but their win was tarnished by the sight of fly-half Joey Carbery being stretchered off with an ankle injury.
Schmidt will hope he recovers before he names his final World Cup squad on September 8, but first has to oversee Ireland's warm-weather training camp in Portugal.
The squad fly out on Wednesday and will stay in camp until their second warm-up match, against England at Twickenham on August 24.
Schmidt says he could take up to 43 players to Portugal in a bid to have as many players as possible ready to step into his World Cup squad should injuries strike.
"I think we'll probably travel [to Portugal] with about 40, but it could be 43," explained Schmidt.
"As you branch off with a smaller squad, just keeping those guys up to speed with what we're trying to develop, it becomes a little bit of a difficulty for us, especially if we pick up an injury.
"We're playing England, Wales and Wales [again], physically big teams, physically bigger than we are, therefore there tends to be a risk of attrition.
"So I don't want those other players to get too far away from us, because we want them up to speed if they do miss out on that 31 in the end."