USA forward Landon Donovan admits he is remaining cautious of an Algeria team he describes as 'unpredictable'.

The US will meet the Africans in Pretoria on Wednesday night and need a win if they are to qualify for the Round of 16 and Donovan knows that the task will definitely be a difficult one.

"It'll be interesting to see how they approach the game," the Los Angeles Galaxy star said. "They have no choice but to win, there are scenarios where we could tie and advance so their approach to the game would most likely be an aggressive approach to get a goal and win the game.

"But they're a team that, as much as we can watch tape and know about their players, as a team they can be unpredictable. On their day they're a very good team. We have to see what the game presents early, but our clear objective is to go out and try to win the game."