American sprint star Fred Kerley maintained his strong start to the season by cruising to victory in the 400m at the Sydney Track Classic on Saturday.

The reigning 100m world champion and Tokyo Olympic silver medallist lived up to his top billing to cross in 44.65 seconds.

Kerley kicked off his season last month with a comfortable 200m victory at the Maurice Plant Meet in Melbourne.

He competed in the 400m for just the fourth time since 2019, having focused on the shorter sprints in recent years.

The 27-year-old was visibly exhausted after the race and remained on his haunches for several minutes.

"It was a good race. I want a good year ahead," Kerley said after the race.

One of only three men in history to run sub-10 seconds for the 100m, sub-20 for the 200m and sub-44 for the 400m, Kerley started modestly before motoring to the front.

He eased up on the back straight to complete a second straight commanding performance in Australia.

However, he fell short of the fastest time in Australia, the 43.84 clocked by compatriot Michael Johnson at the Sydney Olympics in 2000.

Australia's Luke van Ratingen finished second with 46.17.

In-form New Zealander Zoe Hobbs ran a blistering 10.97 to record the fastest women's 100m time on Australian soil while setting a new mark for her country.

"I just wanted to have fun and enjoy the atmosphere... it all came together," said 25-year-old Hobbs, who smashed the event's record of 11.21 held by Australian Sally Pearson.

"I can't believe it. I'm speechless."

Rohan Browning, Australia's fastest man, backed up his 100m victory in Melbourne with a time of 10.14.

He again edged out powerfully built New Zealander Eddie Osei-Nketia, who is set to embark on an American football career at the University of Hawaii this year.