NEW YORK (AP) -- When the U.S. soccer team talks strategy, it sounds a bit like people picking lottery numbers or the start of a keno game: 4-4-2. 4-2-3-1. 4-3-3.
Two weeks before the Americans' World Cup opener, they're still tinkering with their formation.
''There's no such thing as a best system,'' U.S. coach Jurgen Klinsmann said. ''It's the whole team, how it shapes up and how it works as an entire unit, how it attacks collectively and how it defends collectively.''
After replacing Bob Bradley as the Americans' coach in July 2011, Klinsmann most often used a 4-2-3-1 formation: four defenders with two defensive midfielders in front of them. Higher up the field were three advanced midfielders supporting a lone forward.
Jozy Altidore usually was the striker when Klinsmann had his full player pool available, and Clint Dempsey was in the central attacking midfield role or advanced to a withdrawn forward.
But Klinsmann switched to a 4-4-2 for last month's exhibition against Mexico with a diamond midfield that pushed midfielder Michael Bradley into an attacking position and moved Dempsey closer to goal, where he could link better with Altidore.
''It's important to mix it up,'' Dempsey said. ''In the past, maybe I was more withdrawn at times. I'm trying to also be up there and be next to him in terms of just not having him be the only guy that's up top.''
Bradley scored the opener in the 2-2 tie against Mexico and assisted on a goal by Chris Wondolowski, who started on a day Altidore remained with Sunderland in England.
In Sunday's 2-1 exhibition win over Turkey, Bradley set up Fabian Johnson's goal with a brilliant chip on a one-two exchange. Dempsey scored the second goal when a defender failed to clear a cross by left back Timmy Chandler.
But with Bradley farther up the field and Jermaine Jones alone in front of the defense, Turkey had a half-dozen good scoring chances in the first half. Klinsmann then told Bradley to drop back into a flat four midfield alongside Kyle Beckerman in the second half. Still, Bradley had to get higher when the Americans attacked, and a heat map shows he ran constantly between the penalty areas.
''My role? Is in the center of the field, in the center of the midfield,'' Bradley said. ''I try to do as much as possible to help the team, whether it's scoring goals, setting up goals, winning tackles, intercepting balls. I try to have as big an impact on the game as possible. I think when you look around the world now, midfielders who can do everything are so important for their team, so that's what I try to do.''
Bradley, the 26-year-old son of the former coach, has developed into the engine of the U.S. team.
''I think we're starting to see more of the full Michael Bradley,'' Altidore said. ''You saw what he could do on the defensive side. He's very good at winning tackles and distributing the ball. Going forward, he's also very good.''
The U.S. has just two more big tests before leaving for Brazil: an exhibition against Nigeria on Saturday at Jacksonville, Florida, followed by a scrimmage against Belgium on June 12. The Americans open on June 16 against Ghana - which eliminated the U.S. from the last two World Cups - then play Portugal and Cristiano Ronaldo six days later. The Americans close the first round against three-time champion Germany.
''You can win a tournament like Spain did two years ago, play a 4-6-0, leave all the strikers out and have midfielders that score all the goals,'' Klinsmann said. ''Systems in the near future have no meaning anymore, really.''
NOTES: Chandler transferred from relegated Nuremberg to Eintracht Frankfurt, his original club, agreeing to a three-year contract. ... A day after arriving in Jacksonville, players went for a pre-breakfast run on a beach. ... MLS has an all-time high 21 players on World Cup rosters, up from six in 2010 and its most since 19 in 1998. While 19 players were from the U.S. in 1998, 10 are from the U.S. this year.
AP Sports Writers Rachel Cohen and Janie McCauley contributed to this report.