Defending champions Mexico and United States are each one victory away from another CONCACAF Gold Cup title showdown, but the Americans must avenge a 2-1 group stage loss to Panama to get there.
The US team will face Panama and Mexico will meet Honduras in Wednesday's semi-finals of the biennial North American regional football tournament, with the winners advancing to Saturday's championship match in Pasadena, California.
"As we've gone on, we have progressed as a team and we're on this momentum," said USA's Landon Donovan. "We're getting better. I think we're going to peak at the right time."
Luis Tejada scored in the 19th minute and Gabriel Gomez added a penalty kick in the 36th to put Panama on top in their group match. Clarence Goodson answered for the Gold Cup hosts in the 68th minute, but it was not enough to deny Panama a first victory over the United States after six losses and two draws.
"Give Panama a lot of credit. They started the game well, took the initiative to be aggressive and made some early plays," Donovan said. "Some nights you come out flat and you don't get punished and other nights you do. We learned a valuable lesson."
It was the first group-round Gold Cup loss in American history after 24 wins and two draws and sent a message about the improvement of US rivals from Central America and the Caribbean.
"CONCACAF teams are getting better and better. That's a pretty good team," Donovan said.
The Mexicans, who did not face Honduras in the group stage, received a boost Sunday when they were told by CONCACAF that they can replace the five players withdrawn from the team after testing positive for banned substances in training camp doping tests last month. The Mexicans had asked organisers to replace the players because national federation officials believe they inadvertently ingested banned clenbuterol in tainted meat.
"The Mexican National Team shall be permitted to replace the five separated players with up to five other players for the remainder of the competition," CONCACAF said.
In the tournament's 20-year history, Mexico has won five titles compared to the United States three times. Canada captured the crown in 2000 and Honduras won the inaugural crown over USA on penalty kicks in 1991.
Mexico routed the Americans 5-0 in the 2009 final, spoiling the United States' bid for a third consecutive Gold Cup title. The Gold Cup champions earn a berth in the 2013 FIFA Confederations Cup.