USA defender John Brooks has warned that his team still have plenty of work to do to reach the second round of the World Cup following their victory over Ghana.

The 21-year-old came off the bench to score a late winner for the Americans on Monday night as they earned a 2-1 triumph in Group G.

Despite the side starting their campaign with a win, Brooks believes that they must not get complacent.

"It's still a long way off," he told FIFA.com. "First of all we need to keep preparing, stay focused on Portugal and then we'll see."

USA are back in action on Sunday when they face Portugal, who were hammered 4-0 by Germany in their first match of the tournament.