Bielsa's Uruguay come into the match at the Bank of America Stadium in Charlotte following a hard-fought penalty shootout victory over five-time world champions Brazil.
Colombia, last beaten in 2022 by Argentina, thrashed Panama 5-0 in the quarter-finals, led by James Rodriguez who is back at the top of his game.
"(Colombia) are a big rival, they're on a run of positive results, and there's also knowledge among the squad and the manager," Bielsa told a press conference on Tuesday.
"Of course, having played Brazil can only be seen in one way, as the most demanding competition, and so is Colombia.
"It's a team that has strong players, a consolidated system of play and that has a lot of time and collective work behind it, which gives the style a certain unity."
The former Leeds United coach added that he has no "plan B" to stop the Colombian attack, the best in the tournament with 11 goals.
"You imagine the games by preventing the opponent from attacking and trying to attack," he said. "You ask about plan B, but there is no plan B. We have to do the best we can.
"The reality is that you can't predict, but try to do what is most convenient for the type of game you play best.
"Colombia attack better than they defend, but we both know that we have to defend and then God will tell."