Hong Myung-bo's side began their campaign with a promising 1-1 draw against Russia on Tuesday.
But with an impressive Belgium side lying in wait for South Korea's final game, Koo knows a winnable contest versus Algeria carries extra significance.
"We have to defeat them to get to the round of 16," the midfielder said. "We'll concentrate on doing whatever it takes to win."
South Korea have progressed beyond the group phase in two of the last three tournaments.
Having famously finished fourth on their home soil in 2002, they were eliminated at the first stage in 2006 before reaching the second round at the last edition in South Africa.
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