All Blacks aspirant Sonny Bill Williams has undergone minor knee surgery but is expected to return to full training with his Canterbury rugby team within 2-3 weeks.

Williams is scheduled to arrive in Christchurch this week to join his new side ahead of their ITM Cup opener against Hawke's Bay on July 30.

The Canterbury Rugby Union said in a statement that Williams underwent minor keyhole surgery in Brisbane on Thursday, and it was deemed successful.

"He is expected to be able to train fully with the Canterbury team within two to three weeks," the statement said.

"The procedure was recommended to address some minor cartilage damage in his knee. Medical specialists had advised Williams to undergo the procedure now as a preventive measure to avoid future problems."

The New Zealand Rugby Union's medical director and the CRU have been in close contact with Williams' representative on the issue, the statement said.

Williams will be unveiled to the New Zealand media after the Canterbury team's training on Friday.

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