New Moon werewolf Chaske Spencer checked into drug rehab before landing his role in the Twilight sequel, The ENQUIRER has learned.

The 34-year-old actor – who plays wolf pack leader Sam Uley in the vampire blockbuster – kicked an addiction to drugs during a five-week stay at the Northwest Indian Treatment Center, a Native American facility.

"Chaske confided to me that he was up for a role in a ‘really big movie’ and didn’t want to screw it up," fellow patient Ray Martin – who lived across the hall from Spencer during his 2008 rehab stint – told The ENQUIRER.

"He said, ‘If anyone finds out I’m here, it would be the worst thing in the world. It could ruin my career!’"

Spencer – whose first name is pronounced "Chess-Kay" – chose the treatment center in Elma, Wash., because it had a high success rate and was off the beaten track, said Martin.

"Chaske is part Lakota Sioux and part Nez Perce, so he really identifies with the Native American culture," added Martin. "He wanted to get sober in a place with other Native Americans."

During group sessions, Spencer – who’s single and lives in New York City – openly admitted he was a drug addict, but added that he only drank socially and didn’t consider himself an alcoholic, said Martin.

"From the way Chaske spoke in the group, I figured his drug of choice was either cocaine or methamphetamine," said Martin, a member of the Lakota Sioux tribe who said he was in rehab for alcoholism.

"He talked about how he’d get all ‘jittery’ after using. He said that he’d get ‘tweaked out’ and stay locked in his room.

"Then, Chaske said he’d come out and run around all over New York, partying at clubs and jumping from woman to woman. He admitted that he was a womanizer who felt he could get any girl he wanted."

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