Australia and South Africa booked their places in the last four of the ICC U19 Cricket World Cup after winning their respective quarterfinal matches on Sunday.
A magnificent century by West Indies' Nicolas Pooran went in vain as Australia reached its third successive semi-final with a comfortable five-wicket victory here, while South Africa's Aiden Markram scored his second consecutive hundred to take his side to an easy nine-wicket win over Afghanistan in Sharjah.
Australia and South Africa will clash in the second semifinal of the tournament on February 26, while the first one will be played between England and Pakistan on Monday.
Pooram, who came out to bat in the fourth over of the morning with the West Indies tottering at seven for three, was the last batsman out after scoring a scintillating 143 that lifted his side to 208 in 49.5 overs after it had collapsed to 70 for eight at the Dubai International Cricket Stadium.
However, the target proved to be a small one for the Australians who achieved the victory in 46.4 overs for the loss of five wickets after openers Matthew Short and Jaron Morgan put on 107 runs for the first wicket.
At Sharjah Cricket Stadium, Justin Dill's four-wicket burst helped bowl the Asian side out for 197 and then opener and captain Markram hit an unbeaten 105 to guide his team home in 39.2 overs.
The West Indies' decision to bat first after winning the toss badly backfired when it plunged to 70 for eight in the 27th over. At that stage, Pooran, who was batting on 38, changed gears and went on to play one of the finest knocks in the history of the tournament.
Pooran clobbered 14 fours and six sixes in a 160-ball innings and added 136 runs with number-10 batsman Jerome Jones (20).
Pooran's innings was finally ended by fast bowler Guy Walker who finished as the pick of Australia's bowlers with three for 44. Ben Ashkenazi (two for 37) and Thomas Andrews (two for 57) were the other wicket-takers.
Australia, in its run-chase, was never in trouble after Short and Morgan provided their side a 107-run first wicket stand in 21 overs. Even though both the openers departed in the space of five balls, Jake Doran ensured there we no hiccups as the three-time champion reached victory target.
Morgan hit eight fours and a six in a 66-ball 55, Short's 62-ball 52 included four fours while Doran scored 49 not out from 64 balls with three fours.
Pooran, reflecting on his innings, said: "At 70 for eight, I wasn't thinking much. I just wanted to do what my coaches had said, which is to bat, bat and bat, and occupy the crease as much as possible.
"Definitely this is one of the best innings I have played to date, but I am disappointed that we did not win. When you make runs, you want to see your side to win rather than lose."
Markram (in pic above) hit nine fours in a 118-ball innings and featured in an unbroken 158 runs second wicket stand with Kirwin Christoffels, whose contribution was 56 not out from 87 balls with three fours.
Earlier, Afghanistan, batting first after making the right call on the spin of the coin, was rocked by Dill and was bowled out for 197. Dill bagged four for 40, his second four-wicket haul of the tournament, while Yaseen Valli took two for 26 and Kagiso Rabada claimed two for 32.
Afghanistan's innings revolved around captain Nasir Jamal who scored 61 from 95 balls with four fours. Usman Ghani (36) and Ihsanullah (30) were the other notable run-getters.