Bolt, 31, is set to arrive in 10 days to trial at the club's Centre of Excellence in Tuggerah on an open-ended deal to try to force his way into the A-League's first team squad.

He was originally planning to come for just six weeks to prove himself but the club and Jamaican sprint star have reworked the deal to make it open-ended.

And included in the new agreement is the right for the Mariners to have first refusal on offering Bolt a deal, effectively shutting out everyone else.

The club feared there was a chance rival sides might try to scoop the Mariners by snatching Bolt from under their nose if he showed enough potential on the training field.

The 100m world record holder is a walking headline that will bring international news crews to the A-League's door if he proves good enough to play first team football.

Bolt has already trialed at various clubs without success and appeared in celebrity football matches but his ambition to one day play for Manchester United seems unlikely to happen.

However the Mariners are keen to see what he can offer and if he is good enough, they hope to give him a run in the A-League if the price is right.

But a club insider warned rivals: "The training agreement does give CCM the first right to sign Usain. If other clubs want to sign him, CCM are protected here."