MEXICO CITY -- Jeff Van Gundy warned the Americans that they were in for a serious challenge.

To his chagrin, he was right, and the U.S. was handed a rare loss Thursday night, falling to Mexico 78-70 in a qualifying game for next year's FIBA World Cup.

According to USA Basketball, it was only the second loss by the U.S. in 30 games against Mexico, with the other defeat coming in the 2011 Pan Am Games.

Mexico opened with an 18-0 run, holding the U.S. scoreless for the first 5 minutes, 51 seconds and forcing the Americans to miss their first 10 shots from the field.

Francisco Cruz scored 24 points for Mexico, while Orlando Mendez-Valdez added 20 points.

"Mexico dominated us from the start, and that's on me," Van Gundy said. "We were not ready to compete at the level Mexico did. Give them all the credit, they played a great, great game."

Marcus Thornton scored 14 points for the U.S., which is using a roster composed primarily of G League players for the qualifying rounds. Xavier Munford had 11 points, and David Stockton and Reggie Hearn each had 10 for the Americans.

The U.S. lost for the first time in 10 games under Van Gundy, who is coaching this team that is tasked with getting the team of NBA stars that will be coached by Gregg Popovich to the World Cup.

"We can't underestimate how hard it is going to be to play on the road, at altitude, and against a team desperate to qualify for the FIBA World Cup," Van Gundy said leading up to the game. "We have to make sure we match that type of intensity and passion that we know they'll bring."

By the time the U.S. found its stride, it was already in deep trouble. Mexico led 31-10 after the first quarter, then staved off a big second-half rally by the U.S.

Trey McKinney-Jones' basket late in the third quarter capped a 15-1 run and pulled the U.S. to within 53-51. Thornton made a pair of 3-pointers about a minute apart in that burst, and Hearn's 3-pointer early in the fourth cut Mexico's lead to 56-54.

But the U.S. never got the lead.

"In the second half, we competed at a high level, and that high level got us back in the game, but we just couldn't get over the hump," Van Gundy said.

The Americans (4-1), who have already ensured a spot in the second round of qualifying that starts in September, end the first-round series of games Sunday when they go to Havana to face Cuba (0-5). It'll be the first time a U.S. men's national team has played in Havana since the 1991 Pan American Games. Mexico (3-2) also wraps up its first round Sunday, when it plays at Puerto Rico (3-2).

David Huertas had 18 points, Angel Rodriguez and JJ Barea each had 15, and Puerto Rico rallied in the fourth quarter in another qualifying game Thursday to top Cuba 84-80.

Under FIBA's new qualifying format, teams are playing home-and-home games against teams in their region to earn places in the World Cup in China, which begins on Aug. 31, 2019. That tournament will qualify seven teams for the 2020 Olympics in Tokyo.

This was the first time the U.S. played a true road game during this tournament. The Americans opened qualifying in November with an 85-78 win in what was a "home" game for Puerto Rico -- but the contest was actually played in Orlando, Florida, because of continued problems in San Juan following Hurricane Maria.

And this was very much a real road atmosphere.

Not only was the game played at Mexico City's 7,500-foot altitude, but in a filled 5,000-seat arena that Mexican officials said sold out in only 45 minutes.

The tone was set by the U.S. turning the ball over on each of its first three possessions, and Mexico was off and running.

The U.S. routed Mexico back in November, winning by 36 points.

That was a very different Mexico team.

Only four players from the Mexican roster then were in uniform Thursday night, with the team now able to add those who were playing in their various professional leagues and unable to take part when the qualifying rounds began. Cruz and Mendez-Valdez each had 13 points by halftime, and Gustavo Ayon was a big factor even without big numbers -- four points, four rebounds and five assists by the break.

If their names are familiar to U.S. basketball aficionados, it's for good reason.

Ayon appeared in 135 NBA games in parts of three seasons with four different franchises and just helped Spanish powerhouse Real Madrid win the EuroLeague. Mendez-Valdez was part of the Western Kentucky team that went to the Sweet 16 in 2008, and he won the Sun Belt's player of the year award the following season. Cruz played at Wyoming and has played in pro leagues in Mexico, Latvia, Argentina and Spain.