Somerset's Marcus Trescothick and Craig Kieswetter each scored centuries but Gloucestershire emerged victorious by 12 runs on the Duckworth/Lewis method.

Trescothick (184) and wicketkeeper Kieswetter (121) shared a second-wicket stand of 302 as Somerset reached 333-4.

But Gloucestershire were quick out of the starting blocks and had made 236-3 from 28 overs when the rain arrived.

The stand between Trescothick and Kieswetter was a record for any wicket in the 40-over competition.

The former England opener reached his century in only the 24th over, with Kieswetter not far behind.

But both batsmen fell to consecutive balls from Steve Kirby (3-87), with the score on 322.

Kieswetter was caught at cover, having hit nine fours and five sixes off 107 balls, while Trescothick's career-best one-day score, coming off just 112 deliveries, included 20 fours and six sixes.

The Gladiators launched a bucaneering response as Hamish Marshall and Kadeer Ali raced to 89 in the ninth over when the New Zealander was lbw to Stefan Jones.

In the 18th over, Mark Hardinges (80no) hit consecutive sixes into the Botham Stand off Arul Suppiah, only for Kadeer (73) to be run out by a smart return from midwicket by Wes Durston.

With the score on 214 for two after 25 overs, the Gladiators were 24 runs ahead of Somerset's total at the same stage and looked to be cruising to victory.

Justin Langer then ran out Craig Spearman with a direct hit from midwicket to narrow the margin, but Gloucestershire were still comfortably in front when the rain arrived.