Kalyn Ponga has trained well this week, but New Zealand coach Stacey Jones says the fullback must clear more checks before Saturday's semi-final.
Jones has also sought advice from Jahrome Hughes, who returned to play in the 2025 NRL final series just 22 days after arm surgery.
The Storm and Kiwis No.7 told media in Newcastle: "He (Ponga) has to have confidence in his arm and feel right."
"You don't want him going out there and having to worry about his arm... because that will just take away from this game."
Ponga, the Knights captain, is listed on extended reserves after missing New Zealand's past two matches.
He had surgery for a fractured forearm injured in the Kiwis' Rugby League World Cup opener against Australia on October 15.
"He's trained really well this week, including a good session today, so that's another step closer to playing," Jones said.
"We have to get through one more session but Kalyn is looking pretty good."
"At the moment he's doing everything right, he just has to tick a couple more boxes and we'll see where that lands on Saturday."
New Zealand meet Tonga at McDonald Jones Stadium in Newcastle on Saturday night, with a place in the 2026 Rugby League World Cup final at stake.
Kick-off is at 8:05pm.