Costa Rica slowed the USA's march toward the 2014 World Cup with a 3-1 win Friday, while Mexico were on even shakier ground after a 2-1 loss to Honduras.
Costa Rica moved to the top of the six-nation final qualifying group in North and Central America and the Caribbean (CONCACAF) with the victory in San Jose that ended the USA's 12-match winning streak.
The Ticos now head the group on 14 points, one more than Jurgen Klinsmann's United States.
Mexico, long the powerhouse of the region, are in worse straits heading into another crucial round of matches Tuesday.
Two goals in the space of three minutes in the second half lifted Honduras to victory in Mexico City and into third place in the group that will see three teams advance directly to next year's finals. The fourth-placed team play off for a berth against New Zealand.
Mexico, held to three dispiriting goalless draws in their three prior qualifiers at Azteca Stadium -- the venue where they once dominated all comers -- appeared poised to turn things around when Oribe Peralta put them ahead 1-0 in the sixth minute.
But Jerry Bengtson in the 64th and Carlo Costly in the 66th ensured Honduras came away with a maximum three points that take their total to 10, with Mexico fourth on 8.
In San Jose, Costa Rica were out for revenge after a bitter 1-0 defeat to the United States in Denver in March, in a match played in heavy snow.
The hosts jumped to a quick lead as Johnny Acosta beat DaMarcus Beasley on a set-piece corner and headed home a goal in the third minute.
The United states were still reeling when Celso Borges doubled Costa Rica's lead in the 10th, heading in a cross lofted in by Christian Bolanos.
Clint Dempsey's first-half penalty -- after charging Costa Rican keeper Keylor Navas brought down Fabian Johnson in the box -- pulled the United States within 2-1 at halftime.
A more disciplined United States were pressing for an equalizer after the break before Joel Campbell's 75th minute strike restored Costa Rica's two-goal advantage.
US striker Jozy Altidore, still nursing a sore hamstring, came on in the 71st minute, but his bid to make a difference ended with a shot blocked, and the long clearance found Campbell who scored.
"Qualifying is all about ups and downs," said US veteran Landon Donovan, who started the match after a 10-game absence from qualifying action.
"It's never going to be easy. It never is. Every time is hard. So we've got to get ourselves recovered physically, recovered mentally, and we have to beat Mexico now on Tuesday."
Klinsmann, whose team sought to win a qualifier in Costa Rica for the first time, had to make last-minute changes when midfielder Michael Bradley hurt an ankle warming up. Klinsmann said the ankle swelled, and it's not clear if Bradley will be able to play when the United States host a desperate Mexico in Columbus, Ohio, on Tuesday.
Honduras became the first team since Costa Rica in 2001 to win a World Cup qualifier at the Azteca, and their stunning triumph is sure to strengthen calls for the ouster of Mexico coach Jose Manuel "Chepo" de la Torre.
Shouts of "Chepo out" echoed in the stadium as the match ended, but de la Torre insisted he would stick it out, despite what he acknowledged was an embarrassing defeat.
"We are still in the midst of the project," he said. "We have the upcoming matches and we have to get points. On Tuesday, we have to beat the United States.
"Quitting now would be a failure," de la Torre added, "it would be to throw away a lot of work."
Mexico are just one point in front of fifth-placed Panama, who played to a goalless draw against Jamaica in Panama City. The hosts dominated but couldn't capitalize on their one-man advantage in the final half hour after Jamaican Rodolph Austin was sent off.