Waikato insist that forward Jono Gibbes has not yet agreed to join the Ospreys.
Gibbes has eight All Black caps to his name
The Welsh region announced on Tuesday that the 29-year-old back-row cum flanker had signed a three-year deal.
But Waikato Rugby Union chief executive Gary Dawson says they are still trying to keep the Maori, Chiefs and eight-cap All Blacks star in New Zealand.
"Jono is off contract at the end of the year and he's considering his options," said Dawson. "One of them is the Ospreys but he hasn't signed."
The Ospreys say that Gibbes is under contract with the New Zealand Rugby Union until the end of the 2006 season (October) but has requested early release and insist that he has signed.
Jono is a proven leader of men and will bring a wealth of experience to our squad
Ospreys managing director Mike Cuddy
Auckland-born Gibbes captained the Maori to a memorable win over the Lions last year, and won his last All Blacks cap against Clive Woodward's team.
He captained the Chiefs in their Super 14 campaign this year and is currently leading the Maori at the Churchill Cup.
"Gibbes is a top-quality international rugby player and his signing, along with that of Justin Marshall, signals our intent to be a far more competitive team in European rugby next season," said Ospreys managing director Mike Cuddy on Tuesday.
"Jono is a proven leader of men and will bring a wealth of experience to our squad for what is already an eagerly anticipated season."
Meanwhile, the Ospreys have released ex-Wales centre Leigh Davies and Damian Karauna.
Davies failed to make his mark at the Ospreys
Davies has failed to make his mark in a comeback season at the Ospreys, having returned to professional rugby after a gap year of travelling.
Utility back Karauna came to Wales last October with Adrian Cashmore, but the Kiwis failed to make a major impression, Cashmore hampered by a back injury that forced his retirement.
"The end of a season is always a difficult time, but it is vital that you always look to balance and refresh the squad," said Ospreys coach Lyn Jones, who has also seen Andrew Newman, Richard Rees and Rhodri Wells leave the region.
"I would like to thanks each of these players for the contribution they have given to Ospreys rugby."
The runaway 2004/5 Celtic League champions endured a miserable, injury-ravaged 2005/6.
But with the recruitment of the likes of Justin Marshall and probably Gibbes they should have a formidable roster for next season.