By Steve Keating

RIO DE JANEIRO (Reuters) - After two routs to open the Olympic women's basketball tournament, the question is not so much will the all-conquering United States win a sixth straight gold medal but will they ever lose again.

The U.S. followed up their drubbing of Senegal in their opener with a less ruthless but no less clinical 103-63 dissection of third-ranked Spain on Monday, blowing out a team viewed by many as a legitimate medal contender.

It seems as if nothing can stop the U.S. juggernaut as the mighty Americans ran their Olympic winning streak to 42 games, a 24-year stretch of domination dating back to the 1992 Barcelona Summer Games.

"You go into the game thinking that maybe today is the day you can beat them because it is not impossible," offered a hopeful Spanish captain Laia Palau. "You just have to have a wonderful game on your side and they have to be, I don't know, sick."

Spain has never won an Olympic medal, but with an experienced lineup that includes two players earning a living in the WNBA they represented a huge step up in class following a 121-56 mugging of Senegal.

But like nearly every other nation that lines up against the United States, the Spaniards are still searching for their first-ever win.

The two countries have met nine times in Olympic and world championship competition, Team USA winning all nine including their three previous Summer Games encounters by a whopping average of 35 points.

"I haven't been on many underdog teams in my career but I do have an awareness of what it feels like when no matter what you do you have no chance, and it's not a good feeling," said U.S. captain Sue Bird. "But on the flip side there is also opportunity to upset, to make history and that I am sure is in the back of all their minds.

"Would I want to be in their shoes, probably not, but they are trying to make history by beating us."

Despite the difference in pedigree between Spain and Senegal, who are still chasing a first-ever Olympic win, the Group B contest unfolded in much the same fashion.

Playing in front of a small, sleepy crowd at the Youth Arena, the U.S. took a few moments to shake off the cobwebs but quickly turned on the style as they sped to a commanding 54-37 halftime lead.

Once again the depth of Team USA was highlighted with all 12 players getting on the scoreboard, including five in double digits with Diana Taurasi leading the way with 13 points.

"We're not easy to deal with obviously," said U.S. coach Geno Auriemma. "Spain is a pretty good but when you look at our depth it starts to take its toll on the other team.

"That's the pressure we can put on teams, everybody we bring in off the bench can score and make a play.

"It's a good place we are in right now."

(Editing by Meredith Mazzilli)