Sam Allardyce (left) could not stop Michael Owen leaving

The England striker's contract contains a clause which means he can go if a substantial bid - believed to be more than �9m - is received.

Allardyce said: "If Michael wants to go there's nothing I can do, if another club triggers his release clause.

"We're benefitting from a release clause to get Joey Barton, but we could also suffer because of Michael's."

Allardyce arrived at St James Park with speculation surrounding Owen's future on Tyneside.

The England international arrived at Newcastle in the summer of 2005 in a �17m move from Real Madrid.

But his two years on Tyneside have been racked by injury, restricting him to a handful of games.

But Owen appears to be winning his fitness race and was recently restored to the England squad, 11 months after seriously injuring his knee during the 2006 World Cup.