(Reuters) - Great effort and determination have long been the foundation of American teams and the United States showed that spirit again at this World Cup but, as their second-round exit to Belgium showed, those qualities can only take you so far.

Coach Juergen Klinsmann squeezed everything he could out of his squad in this tournament and his words of pride for the players were sincere and justified.

But when he sits down to plan the next four years he will surely be looking for the missing ingredients that would make a hard-working, strong and gutsy unit into a team capable of going deeper into the latter stages of the World Cup.

The missing elements were evident in all of the United States' games in Brazil - a lack of creativity and a killer touch in attack.

Klinsmann's midfield was packed with players who worked hard, tackled, covered ground and kept the ball moving. None did that better than German-born Jermaine Jones while Kyle Beckerman was an effective anchor in front of the defense.

Neither were able to reproduce their form from the group stage against Belgium - Beckerman didn't start and Jones looked to be paying the price of his extraordinary work in the first three games.

But with a disappointing Michael Bradley, so long the engine of the U.S. midfield, never able to produce his best form in Brazil, there was little imaginative about the Americans.

The best moments in the group stage came from the overlapping right-back Fabian Johnson, a player who caught the eye of many with his speed and touch down the flank

Wide midfielders Alejandro Bedoya and Graham Zusi did their jobs diligently but neither are the kind of players who can slice open a defense at this level with an inspired pass or a clever dribble.

The U.S team has no classic number ten, no playmaker, no fearsome winger and no-one in their midfield who would cause an opposition coach to consider changing his own tactical approach.

SEEKING THE SPARK

Up front, Jozy Altidore's hamstring injury against Ghana left Klinsmann relying on Dempsey as a lone striker for the rest of the tournament. Dempsey has proven his worth over the years for his country but he is far more effective as a support striker, roaming off a center forward.

Klinsmann clearly didn't believe the other strikers in his squad, Aron Johannsson and Chris Wondolowski, were the right men to lead the line. The latter's miss in the final seconds of regular time against Belgium might have confirmed his instincts.

If this U.S. team had a quality striker and a genuinely inspired midfielder they might be preparing for a quarter-final against Argentina rather than heading home.

Klinsmann, who is also technical director of the U.S. Soccer Federation and has gained impressive control over the system, will surely now be focusing on trying to find those kinds of players.

Traditionally, the United States are good at producing hard-working and athletic players but the youth development and college system have been less effective in uncovering talent that can do the things that can't be coached so easily.

Somewhere among the thousands of young players in the United States there may be, if not an American Lionel Messi or Cristiano Ronaldo, a player or two with the talent of Colombia's James Rodriguez.

The strong growth in domestic interest, with record television ratings for this tournament, can only help in that process. Coaches and scouts from U.S Soccer and clubs in Major League Soccer need to take a smart approach to finding talent.

But even as this particular American dream was dying in Salvador, there were already some pointers towards a more exciting American team of the future.

Twenty-year-old wing-back DeAndre Yedlin impressed with his confidence and speed against Belgium and 19-year-old substitute Julian Green came on and made an instant impact, including a beautifully taken goal that prompted a late fightback.

The Americans are now established as a top-20 force in the world game, the question is how quickly they can find the talent to take them into the top ten and beyond.