James' feat in outscoring Italy's European champion, Giacobbe Fragomeni, gives Britain their first medal in the 25-year history of the championships, although Ireland have won four bronzes.
But James must climb a mountain in today's semi-final when he tackles the formidable Cuban Felix Savon, who has won the gold medal in the previous six championships stretching back to Reno in 1986, in addition to landing the last two Olympic 91kg titles.
Otherwise it was all gloom for British boxers. The big medal hope Audley Harrison lost his second bout and England's light-middle Chris Bessey was beaten, as was the Scottish featherweight Alex Arthur.
James, a 22-year-old from Carmarthen, outscored Fragomeni by 9-7, but it was a debatable decision which received a mixed reception from the crowd. The Welshman, now the only Briton left in the tournament, was on the receiving end in the fourth, but managed to hold on to his narrow verdict.
Harrison, a 6ft 5in, 18st 7lb medal prospect for the Sydney Olympics, went down 4-3 against Turkey's Siren Samil, ring-rustiness catching up with the Repton super-heavyweight, who intends to turn professional after the Sydney Olympics.
Harrison's one bout since winning the gold medal in the Commonwealth Games in Kuala Lumpur 11 months ago was in these championships. A hernia operation has kept him out of the ring since.
He said: "I'm not making any excuses, I know I am still learning at this level. I'd set my goals on a medal and I was two clean punches from that. However, I feel I'm still on course to win gold in Sydney."
Edinburgh's Arthur lost 5-1 to the local boy Ricardo Juarez in his third bout. The Scottish stylist needed to keep the American body puncher at long range, but the Commonwealth champion felt the pace after a tough bout in the previous round against Australia's non-stop James Swann.
Bessey, a European bronze medallist and five-times ABA champion, put on a brave show against Romania's Marin Simion. But the Portsmouth soldier was beaten by the wide margin of 13-2.
The Matchroom promoter Barry Hearn wants to stage a WBO featherweight re-match between Naseem Hamed and his predecessor as champion, Steve Robinson, at the Millennium Stadium in Cardiff next summer.
Hearn, in Cardiff to publicise Robinson's European defence against the French champion Claude Chinon at the International Arena on 2 October, expects the local man to become Hamed's mandatory challenger in the next few weeks. Hearn said: "The Mexican currently ranked number one, Juan Manuel Marquez, is due to fight for the WBA version, so, according to the WBO rules, Steve should move up from number two."Reuse content