A FORMIDABLE 50-strong professional field leading some 800 competitors in the inaugural Ironman 70.3 Asia-Pacific Championship at Laguna Phuket was blown away by a devastating performance from American Tim O'Donnell, who held a surging lead throughout to finish the challenging new triathlon course a shade under four hours and claim the $12,000 title.

Former US Navy lieutenant O'Donnell attacked the race with military precision, saving precious seconds on the bike course by adopting a cyclo-cross style to carry his bike and run the descent of the unique road bridge cross-over, while the rest of the field opted to continue their dismounted push.

First out of the water from the 1.9km swim in 00:24:34, O' Donnell, rounding off an impressive 2010 season which has included the Ironman 70.3 Florida title, stretched his lead on the gruelling 90km bike course with a time of 02:13:04, and finished the 21.1km run in 01:19:44 for a total time of 03:59:42.

A battling performance by Massimo Cigano, winner of last weekend's 17th annual Laguna Phuket Triathlon, saw the Italian claw his way through the leading pack to finish second in 04:01:52, just over two minutes behind O'Donnell. He was followed in by Hideo Fukui of Japan in 04:04:00.

''This was my first time to race in Phuket and this is a truly world-class event,'' said O'Donnell.

''The bike course was unbelievable with some really tough hills, but all the support from the spectators really got me pumped up. I'd done my homework on the bridge bike dismount; I had a plan to get across fast and efficiently, and it worked.''

In the women's field, Switzerland's Caroline Steffen continued her meteoric rise through the international triathlon ranks with a precision performance to clock up her fourth Ironman 70.3 title this year.

Ironman World Championship runner-up in Hawaii, the powerful Steffen - self-styled 'Xena, the Warrior Princess' - fought a ding-dong battle with 13-time Ironman champion and last weekend's Laguna Phuket winner Belinda Granger on the steep inclines of the bike course, before pulling away from the Australian to shave a lead entering the run.

She then proved too strong for the chasing pack, finishing nearly five minutes ahead of nearest rival Melissa Rollison of Australia, who overhauled Granger on the run.

Steffen, also making her debut in Phuket, completed the triathlon with a swim of 00:26:31; bike ride of 02:23:03 and a run of 01:27:17 for a total time of 04:20:13. Rollison finished second in 04:24:53, and Granger held off a late challenge from fellow Australian Michelle Wu to take third place in 04:30:49.

Steffen, who spent two weeks in nearby Krabi preparing for the Ironman 70.3, said: ''I'm thrilled to win such a fantastic challenge. It's such an exciting course with unique features, like the bike bridge and the swim in both sea and across fresh water - it's just an amazing place to compete in triathlon.''

First Thai male finisher was Jaray Jearani in 05:02:03; and first Thai female was Mayuree Maidaeng in 05:21:33.

The inaugural Ironman 70.3 Asia-Pacific Championship saw nearly 50 professional athletes, among some 800 amateur competitors from 51 countries, race for a share of the prize purse of $75,000.

Winners in professional male and female categories each received $12,000; second place $8000; third $5500; fourth $4000; fifth $3500; sixth $2000; seventh $1500; and sixth US$1000.

The spectacular race was the climax to a week which began with the Laguna Phuket Triathlon on November 28 and continued with a carnival of daily sporting and social events for the triathlon professionals and hundreds of amateur devotees gathered on Phuket.