The 20-year-old, who was named in England coach Shaun Wane’s squad earlier this year, was injured attempting a tackle 30 minutes into the match at Warrington’s Halliwell Jones Stadium.
The game was held up while Newman had treatment on the pitch before he was carried off on a stretcher and taken to hospital.
Leeds coach Richard Agar said: “He’s definitely broken his leg, his tib and fib we think.
“We feared he had broken his hip as well but they’re saying it settled down in the ambulance.
“He’s having x-rays and they will tell us what the next step is but it will be a three to six-month job.
“It’s a huge blow for him and we’ll do our utmost to keep his spirits high. Typical of Harry, as he was coming off, he gave the thumbs up to the stand. He’s a great kid, we love him to bits.”
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