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Player of the tournament when Australia won on home soil four years ago, Starc looked in fine form in two rapid spells that each netted wickets for an Australian XI against New Zealand on Wednesday.
Smith's unbeaten 89 was the other good news story for Australia despite the Black Caps chasing down their 6-277 with seven wickets and 16 balls to spare at Allan Border Field in Brisbane.
Kane Richardson, who will replace the injured Jhye Richardson in the squad for next month's tournament in England, said Starc hit speeds close to 150kmh in a showing that adds plenty to the side's Cup defence.
"I was sitting near the speed gun ... I think 148(kmh) one of them was, the rest of us were around 135," he said.
"I think if he bowled his quota it (the result) may've been different.
"It's the trump card to have at that last World Cup; sitting back watching that was pretty amazing."
Starc (2-14 from five overs) was the only wicket-taker in a below-strength attack as Will Young was run out for a superb 130 and captain Tom Latham (69no) saw New Zealand home.
Smith had early powered Australia's innings, slowly working into top gear in his second game in Australian green and gold since the Cape Town 'sandpaper-gate' scandal.
His innings followed a six-ball duck in Warner's return to the top of the order - he batted at No.3 on Monday - as coach Justin Langer ponders his opening options ahead of their World Cup start in Bristol on June 1.
The hosts had snuck home by one-wicket in the first of three warm-up games on Monday against the understrength Black Caps and mixed up their side on Wednesday.
Pat Cummins, Nathan Coulter-Nile and Jason Behrendorff were all rested after taking nine wickets between them in the opener.
More important than the result, Starc steamed in untroubled in his return from a pectoral injury.
He took a wicket in his first over and broke through later with a trademark yorker before the visitors ran away with it.
Warner hit the nets as soon as he was dismissed while Smith shared fluent partnerships with Glenn Maxwell (52 from 44) and Usman Khawaja (56 from 75), after Shaun Marsh (28) wasted his good start.
Young and Latham made the chase look comfortable as Richardson, Sean Abbott, Michael Neser, Nathan Lyon and Maxwell all struggled to make an impact with the ball.
Richardson finished with 0-52 from 10 overs after also going wicketless in Monday's match in what he described as a much-needed hit out after two weeks off and two weeks of training in an indoor centre.