Paulo Bento needs Germany to do Portugal a huge favour after a 2-2 Group G draw with the United States left his side teetering on the brink of early World Cup elimination.
The Seleccao would have been knocked out of the tournament by the USA had substitute Silvestre Varela not scored a last-gasp equaliser in Manaus.
Nani opened the scoring during the early exchanges at the Arena Amazonia but the USA hit back with goals from Jermaine Jones and captain Clint Dempsey. However, Varela salvaged a vital point for his side.
Portugal must now beat Ghana in Brasilia while hoping group leaders Germany inflict a heavy defeat on the USA.
Bento told FIFA.com: " It's clearly not a good result for us. The 2-2 doesn't put us out of the World Cup mathematically, but it does leave us in a very difficult situation.
"Not just because of what we'll need to do against Ghana, but also because we'll need a favourable result from the Germany-United States game.
"We were unlucky late in the first half, but it was a great effort to level the match (in second-half stoppage time).
"Now all we can do is to give everything in our very last game and try and make the most of the very little chance that we have left."
The USA, who beat Ghana 2-1 last week, came so close to recording back-to-back wins but, despite admitting he was frustrated by Sunday night's result, coach Jurgen Klinsmann hailed an "extraordinary performance".
"When you concede a goal in the last second then it's unlucky," he said. "Our boys put in an extraordinary performance.
"The journey's now a little bit longer for us, but we want to beat Germany to confirm our place in the round of 16.
"I'm a little frustrated with this draw, but we're going to work hard to make sure this doesn't happen again."
Everton goalkeeper Tim Howard pulled off a series of fine saves to keep Portugal at bay during their brighter periods.
He said: " We're a little disappointed, but still optimistic.
"We thought we'd put one foot in the round of 16, but we are where we'd aimed to be before the tournament: going into the final game with a good chance of progressing.
"The coaching staff put in place a great game plan. Portugal didn't cause us too many problems and we could have avoided both their goals.
"We moved the ball around better and had the clearer chances. We're not going to let the last-gasp goal get us down."
On Thursday the USA meet Germany in Recife, where a draw will be enough to send both nations through to the knock-out stages at the expense of Ghana and Portugal.