Australia needs seven wickets to win the first Test against West Indies, who must survive one more day, requiring a nominal 306 more runs to win at Perth Stadium.
Another magnificent Marnus Labuschagne century helped Australia to 2-182 at lunch on day four — a lead of 497 runs — before declaring and starting its quest for 10 wickets to win.
But the home side had to do it without skipper Pat Cummins, who was rested for the first session of the innings with a quad strain, but returned later in the day with hopes of bowling on day five.
The captain's absence left Australia a bowler light early in its attack and West Indies openers Kraigg Brathwaite and Tagenarine Chanderpaul weathered the weakened storm, putting on 116 for the first wicket.
Brathwaite made his way to a fighting, brilliant century on day four, but Chanderpaul eventually fell to an around-the-wicket plan of attack from left-arm speedster Mitchell Starc, chopping on for 45, falling just short of dual half-centuries in his first Test.
Incredibly, Josh Hazlewood clipped the top of Brathwaite's off bail at 130kph when the Windies skipper was on 67.
A superb piece of bowling from Nathan Lyon nicked off concussion substitute Shamarh Brooks (11) and he almost found the edge of Blackwood's bat two balls later, the faintest of a murmur on snicko not enough to overturn the umpire's decision of not out.
Blackwood was saved by his own review and Perth's high bounce after he was given out LBW in the next over, but ball-tracking showed he was hit too high.
Blackwood survived one more Australian review — for caught behind off Cameron Green — before eventually edging Lyon to Labuschagne at short leg with just a few minutes left in the day's play.
It put more pressure on Brathwaite to be the man in the fourth innings as he made it to stumps alongside Kyle Mayers on a pitch that is not breaking apart as Perth pitches sometimes do, with Australia desperate to make up for a series of fourth-innings struggles with the ball in recent times.
Marnus ticks off another bit of history
Earlier in the day, Labuschagne achieved something very few batters have in the history of Test cricket.
He is just the eighth man to score a double century and a century in a single Test match, joining greats Doug Walters (Australia), Sunil Gavaskar (India), Lawrence Rowe (West Indies), Greg Chappell (Australia), Graham Gooch (England), Brian Lara (West Indies) and Kumar Sangakkara (Sri Lanka).
He did it at a ground in which he has never failed to raise the bat in Tests, registering scores of 143 and 50 against New Zealand in 2019, to go with his 204 and 104 not out in this match.
Neither he or Australia had it all their own way though in the first hour, as Alzarri Joseph (0-42) unleashed a fearsome barrage of short-ball bowling to terrorise Labuschagne.
Resuming on 1-29, Australia's two batters had to fight for every run under serious duress from the pace of Joseph and Kemar Roach (1-30).
It appeared as though that tactic may have paid off too, when Labuschagne top edged a vicious bouncer onto his helmet, with the ball ballooning up to gully.
However, replays showed that Joseph had overstepped by the narrowest of margins, much to the frustration of the fired up Antiguan quick.
Labuschagne was on 17 at that stage and continued to weather a storm from Joseph, ending up on his backside on more than one occasion when trying to avoid getting hit.
However, once he settled the runs started flowing, including two sublime drives off the little-used Jayden Seales (0-18), the opening bowler managing just three overs due to an injury.
West Indies was also without the bowling services of Mayers and — in the latter part of the morning — Roach, who suffered a hamstring strain.
David Warner (48) got to within two runs of a welcome half-century before being caught at bat pad off the bowling of Roston Chase, his eighth innings without a fifty in Test matches in Australia.
His departure bought Smith to the crease and the start of an hour of sublime limited-overs-style hitting.
Smith though played second fiddle to Labuschagne, nursing him towards a ninth career Test century in the final over before lunch, which brought with it Australia's second declaration of the match.
