Pakistan's Mohammad Amir took a one-day international best five for 30 on Wednesday as David Warner made his first international century since completing a ball-tampering ban in Australia's total of 307.
Australia looked set for a huge total in Taunton while Warner and captain Aaron Finch (82) were sharing a first-wicket stand of 146 — the highest partnership for any wicket at this World Cup to date.
But left-arm quick Amir dragged Pakistan back into the game, returning figures that surpassed his previous best of 4-28 and are the best in the tournament so far.
"I think I left a few (runs) out there," admitted Warner during the break between innings. "The second spell from Mohammad Amir was fantastic.
"We have got to come out and bowl Test match line and length and be very disciplined."
Both Warner and Steve Smith, also returning from a year-long ban for ball-tampering, had been jeered by fans in previous games but Pakistan fans largely heeded an appeal from captain Sarfaraz Ahmed not to boo the pair, preferring to roar chants of "Amir!, Amir!".
Amir was on target right from the start after Sarfaraz won the toss on an overcast morning at southwest county Somerset's headquarters.
He started with a probing maiden -- one of two in an initial four-over spell that cost a mere 11 runs.
Finch should have been out for 26 when he edged Wahab Riaz, only for first slip Asif Ali to floor a head-high catch
He was dropped again on 44 when wicketkeeper Sarfaraz could not hold a tough chance following an edged cut off Mohammad Hafeez's second ball.
Finch cashed in, hitting off-spinner Hafeez for two successive fours as he completed a 63-ball fifty.
The skipper then hoisted Hafeez for two legside sixes in as many balls but he gave his wicket away when he miscued a big shot immediately upon Amir's return, with Hafeez taking a fine catch running back from cover.
Smith (10) holed out off Hafeez before Glenn Maxwell (20), promoted up the order to number four, was clean bowled going for a booming drive off Shaheen to leave Australia 223 for three.
Warner completed his 15th one-day international hundred when an outside edge off Shaheen flew past Asif at slip for his 11th four in 102 balls and he leapt in the air in celebration.
But he was out soon afterwards, caught at deep point by Imam-ul-Haq off Shaheen, having gone past fifty for the third time in four innings at this World Cup.
Batsmen Shaun Marsh, Usman Khawaja and Alex Carey all fell to Amir, who ended the innings with an over to spare when tailender Mitchell Starc holed out.
In reply, Pakistan slipped to 56 for two in the 11th over. Fakhar Zaman fell for a duck when he cut Pat Cummins straight to Kane Richardson at third man.
Babar Azam was in superb touch, with 28 of his 30 runs coming in fours, before he failed to get over the top of a Nathan Coulter-Nile bouncer and was also caught by Richardson, now at deep backward square leg.
Feature image courtesy: AFP Photo/ Saeed Khan