Petty (nee Smit) will again battle Hamblin, who has the best 1500m time of the year by a Kiwi after she clocked 4m 10.16s at last month's Auckland Track Challenge.
Like a host of other New Zealand athletes, Petty will head to the Sydney Track Challenge next week when she wants to run under 2m01s for the 800m, which would see her qualify for August's world championships in Beijing.
Petty registered 2m 01.81s at the Canterbury Championships in Timaru last month, despite having little competition in the race.
A pulsating hammer throw competition between 20-time champion Phillip Jensen, 47, and young pretender Matthew Bloxham, 18, was a highlight of the day. The lead changed numerous times, with Jensen edging his way to the lead with a throw of 61.23m in the fifth round, just shy of his winning distance at the 2014 championships.
But Bloxham wasn't done, unleashing a personal best 63.50m on his final throw to deny Jensen his 21st title.
"Today I competed in the NZ national athletics champs for the last time," said Jensen, who won his first title in 1988, eight years before Bloxham was born. "I committed to keep competing at the national champs until I was beaten, and today that happened.
"I'm very excited the title was won by a great talent, who I'm expecting to continue on to greater things. For me, as my children said to me after the competition, RIP - retire in peace."
Other notable performances in Wellington yesterday included a 15th national javelin title for Stuart Farquhar. The 32-year-old tossed 78.17m, which was a few metres below his best of the year but the high winds were never going to allow for a top throw.
Rising prospect Ben Langton-Burnell threw 74.24m to claim second.
Long jump world record holder Mike Powell, who is in New Zealand for two weeks to help promote athletics, was unable to compete as he looked to set a masters age-group world record. The 51-year-old American, who produced a record-setting leap of 8.95m in Japan in 1991, which still stands, was after the 50-54-year-old mark of 6.84m but pulled out when he experienced pain in his hip during his warm-up.
"I'm not giving up by any means," he said of his pursuit for the masters record. "But it's just frustrating."
Today will see the shot put duel between defending champion Tom Walsh and Jacko Gill. The pair rarely compete against each other so their showdown shapes as the most entertaining battle of the weekend. Olympian Nick Willis is set to contest the 1500m final - an event he last won in 2008.
