Sonny Bill Williams stays in union

Sonny Bill Williams has knocked back offers to return to the NRL to stay in rugby union.

Williams has signed a three-year with the New Zealand Rugby Union and Super Rugby franchise the Auckland Blues.

The former NRL star will appear in the Rio Olympics this year in the rugby sevens and then aim to win a third Rugby Union World Cup in a row with the All Blacks.

The Roosters had been after Williams to entice him back to the NRL.

The code-hopper turns 31 in August and appears set to finish his career in the 15-man code.