Backstroke specialist Corey Main has made an important career breakthrough by qualifying for a final at the swimming world championships in Budapest.

New Zealand 22-year-old Main secured the eighth and final spot for the men's 100m final on Tuesday after two strong swims.

Main was ninth fastest in the morning heats with a personal best time of 53.97 seconds. He lowered that again in the semi-finals with 53.76sec, storming home with an impressive second length of 27.54sec.

Florida-based Main has made regular appearances in 100m and 200m semi-finals at major international meets - including the 2015 world championships and last year's Rio Olympics - but had routinely failed to advance to the last eight.

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Olympic silver medallist Xu Jiayu dominated both sessions, clocking a slick 52.44sec in the semi-finals.

Main has closed to within 0.44sec of the national record set by Wellingtonian Gareth Kean five years ago.

New Zealand's four other swimmers in action on Monday failed to advance past the heats.

The best of them was Emma Robinson, 11th quickest in the 1500m freestyle in 16min 25.78sec.

She was three places and 5sec outside a berth in the final.

Double Olympian Matt Stanley was a disappointing 29th fastest in the men's 200m freestyle, in a field of 73, while Natasha Lloyd had the same outcome in the women's 100m breaststroke.

Freestyle specialist Gabrielle Fa'aumausili was ranked 26th among 59 women in the 100m backstroke.