KINGSTON • Usain Bolt will embark on the first major test of what he plans to be a triumphant swan-song today as the Jamaican Olympic athletics trials get under way.

With less than 40 days to go before the Olympics, the sprint superstar will aim to seal his ticket to Rio as he targets a defence of his 100m, 200m and 4x100m crowns.

Bolt, who completed an unprecedented second consecutive set of victories in all three events at the London 2012 Games, is hoping to complete a remarkable "Triple Triple".

So far this season, the signs have been encouraging that Bolt is firmly on track, with the 29-year-old clocking a blistering 9.88sec at a meeting in Kingston on June 11, the second-fastest time in the world this year.

Only France's Jimmy Vicaut, who clocked a wind-assisted 9.86sec earlier in June, has run faster this season.

Unlike the International Association of Athletics Federations (IAAF) World Championships, there are no byes to the Olympics and under the rules of the Jamaica Athletics Administrative Association (JAAA) rules, every athlete seeking to be chosen for the Rio Games must compete at the trials.

Bolt's main challenge is likely to come from Yohan Blake and Nickel Ashmeade, both of whom have clocked under 10 seconds this season at 9.94sec.

With Bolt and Blake favoured to take two of the 100m berths, Ashmeade will likely compete with Asafa Powell and Kemar Bailey-Cole for the third spot.

And while Bolt has yet to run a 200m race so far this year, he will start as favourite to win over the longer distance. Ashmeade, the fastest Jamaican so far this year at 20.07sec, Julian Forte, Warren Weir and Commonwealth Games champion Rasheed Dwyer are all in the mix.

Heats begin today at Kingston's National Stadium with the final set for tomorrow.

AGENCE FRANCE-PRESSE