Goals from Lee Jung-hyub and Kim Young-gwon sealed South Korea's place in Saturday's showpiece, keeping alive their dreams of a third title.
Stielike and his team must now wait to see whether Australia or the United Arab Emirates will join them in the final, but the German is confident he can predict the outcome of the second semi-final.
"Australia, I have no doubt about it," he said. "Australia are the strongest team in the tournament.
"They play very good and very coolly, each player knows exactly what he has to do. They have very strict tactics and so, to me, there's no doubt about it that Australia will go through."
South Korea and Australia have already met in the competition's group stage – the former winning 1-0 – but Stielike expects an even tougher encounter were they meet again in Sydney.
"We will have to work to be the same Korea," he added. "This is our target. For the rest, we have to take whatever is coming and try our best.
"We are realistic that in the first game we didn't play the best Australia team."
Australia meet the UAE in the second semi-final in Newcastle on Tuesday.
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