Barnes outclassed his Japanese opponent on Wednesday

The 20-year-old outclassed Japan's Kenji Ohkubo 24-6 to seal his place in the quarter-finals in Chicago and guarantee an Olympic berth next year.

Other Irish fighters Kenneth Egan and Eric Donovan missed out in their bids to secure Olympic places.

Lightweight Donovan and light-heavy Egan were defeated in last-16 contests.

Donovan was beaten 28-21 by Domenico Valentino, having claimed a win and a defeat in his two previous contests against the Italian.

Egan lost 18-16 to Croatia's Manjo Sivolija.

Ireland's high performance director Gary Keegan paid tribute to the achievement of Holy Family fighter Barnes.

"We have found it hard to get Paddy bouts this year because there are not too many light-flyweights around and we had to think hard about picking him for the squad," said Keegan.

"But the fact that he hasn't experienced the limelight before is working for him.

"He thinks it's all normal and I don't really want him to discover that it's such a big deal."

Darren Sutherland and John Sweeney lost their last-16 contests on Tuesday night to dash their hopes of qualifying for Beijing.

Russia's Rakhim Chakhkiev beat Sweeney 28-5 while Sutherland lost 20-13 against Venezuela's Alfonso Blanco.