Kendall Waston scored in the fifth minute of second-half stoppage time, giving Costa Rica a 1-1 tie against visiting Honduras on Saturday at San Jose and clinching the Ticos' second straight World Cup berth and fifth overall.
The dramatic late goal means the United States likely needs at most a draw at Trinidad and Tobago on Tuesday night to qualify for its eighth straight World Cup berth.
In a match postponed a day because of a tropical storm, Eddie Hernandez's header from Romell Quito's cross put Honduras ahead in the 66th minute.
In the fifth of a minimum six minutes of stoppage time, a long ball from deep in Costa Rica's end was headed from about 23 yards out by Hernandez.
Giancarlo Gonzalez headed the ball toward the right flank, where Bryan Ruiz flicked the ball ahead of Rodney Wallace who, marked by Bryan Acosta and Emilio Izaguirre, played the ball back to Ruiz.
Draw would be enough for U.S.
Ruiz played the ball from his left foot to his right to fake his way past Acosta, dribbled past Izaguirre and crossed to Waston. The Vancouver Whitecaps defender outjumped Maynor Figueroa and Johnny Palacios to head the ball past goalkeeper Donis Escober from 8 yards.
Waston has three international goals, including one on March 28 that gave Costa Rica a 1-1 draw in qualifier at Honduras.
Costa Rica has 16 points and is second in the final round of North and Central American and Caribbean region behind Mexico, which has 21 points and clinched last month.
The U.S. is at 12 points following its 4-0 win Friday over Panama and would qualify with a win at Trinidad on the final night of the hexagonal. Panama and Honduras have 10 points each.
Goal difference has become key: the U.S. is plus-five, Panama minus-two and Honduras minus-seven.
A draw would be enough for the U.S. to qualify unless Honduras defeats visiting Mexico by at least 12 goals or Panama beats visiting Costa Rica by at least seven or eight goals, the needed margin depending on whether it overcomes its deficit to the U.S. in total goals, currently nine.
In addition, the U.S. could qualify with a loss if Panama and Honduras both fail to win Tuesday.
The fourth-place nation advances to a home-and-home playoff next month against Australia or Syria.
The Americans would be eliminated only if they lose and Panama and Honduras both win.