Jessica Hull has declared she can win Olympic gold in the women's 1,500 metres "mega-final" in Paris.

On the basis of what happened in the semifinals on Friday morning (AEST), it seems a perfectly fair call to make.

The pace was hot and Hull looked supremely comfortable running in the top three throughout, crossing the line in 3 minutes 55.40 seconds — her second-fastest time ever.

Ethiopian Diribe Welteji edged Hull for first spot, but the Australian appeared to have more left in the tank.

If she is to become the first Australian since Herb Elliott in 1960 to win Olympic 1,500m gold she will have to find a way past legendary Kenyan Faith Kipyegon, who won the other semi.

"I do (believe I can win the gold)," the 27-year-old Hull said.

"It's the greatest time for the 1,500m ever, we're saying 3:56 just to make the final from that heat so that's insane.

"It's a privilege to be in the position where people are talking about me as a medal contender, let alone a gold medal contender.

"Faith is not going to go down without an absolute fight, the Ethiopians are ready as well, so it's going to be a mega-final on Saturday night."

Hull has taken giant strides forward in the last 12 months.

She was seventh in last year's world championships final and later acknowledged she didn't have the pace to go with the likes of Kipyegon when the heat was really on.

That's no longer a problem, as evidenced by Hull's blistering run of 3:50.83 at last month's Paris Diamond League meet which lifted her to fifth spot on the all-time list.

"Physically it feels incredible," she said.

"Emotionally I'm just so much more mature.

"When I see those splits I'm like 'I've been here before' and I literally have.

"I've done things that a lot of these women haven't done, so that's a power to me when I'm out there."

Fellow Australian Georgia Griffith ran near the front for much of the other semi before running out of gas in the last 50m and fading to ninth.

Earlier in the day, both of Australia's 4x100m relay teams came up just short in their bids to qualify for the finals.

The women's line-up of Ella Connolly, Bree Masters, Kirstie Edwards and Torrie Lewis clocked 42.75 seconds, significantly slower than the flying national record time of 42.48 they ran at the London Diamond League meet in late July

Crucially, the squad anchored by Australian individual 100m record holder Lewis finished outside the top three automatic qualifiers in fourth place and the second heat was faster.

The Australian men's 4x100m squad overcame the absence through injury of national 100m champ Sebastian Sultana to lower the national record in the men's heats.

Their time of 38.12 would have been enough to win the second of the two heats, but unfortunately they were drawn in the much quicker first one where they finished sixth.

Michelle Jenneke defied a ruptured hamstring tendon to contest the repechage round in the women's 100m hurdles.

She trailed home last in 13.86 — well over a second outside her personal best — but was proud of herself for fronting up after sustaining the injury in a heavy fall during the opening round.

Fellow Australians Liz Clay and Celeste Mucci also came up just short.

"I knew that making that semi-final and running under 12 seconds missing one of your hamstrings was probably pretty impossible," the 31-year-old Jenneke said.

"But I just wanted to prove to myself and the rest of Australia that I've got some grit in me and I'm not going to give up easily."

Jenneke will likely have surgery on the ruptured hamstring when she gets home but remains keen to push on until next year's world championships in Tokyo.

Tokyo Olympics fourth-placegetter Peter Bol and national record holder Joseph Deng were run out in the 800m repechage round.