Lionel Scaloni's side are facing the possibility of tumbling out of the competition after being held to a 1-1 draw by Paraguay in Group B on Wednesday.
Messi scored a second-half penalty to cancel out Richard Sanchez's goal in Belo Horizonte, while Argentina needed Franco Armani to save a Derlis Gonzalez spot-kick to preserve their first point of the tournament.
Even a win over Qatar on Sunday may not be enough for Argentina, but Messi said there was plenty of confidence in his team.
"I see the team convinced that we will win the next match," he told reporters.
Messi added: "We have to keep looking for the team and improve.
"Frankly, it's a little frustrating not being able to get the win we need to take the next step.
"We knew this would be difficult, we're still looking for the best group, for the best performance, to keep growing."
Argentina struggled throughout the first half and fell behind to Sanchez's 37th-minute goal, before Messi equalised after a penalty was awarded following a VAR review for handball.
Armani stepped up for Argentina in the 63rd minute, though, diving to his left to push away a Gonzalez penalty.
Messi felt his side earned their point, saying: "The first few minutes we managed the ball well.
"After the goal, we messed up a bit. In the second half, we went with everything and we got the draw."
The five-time Ballon d'Or winner is confident that Argentina will raise their game when it matters, with a humbling departure from a tournament on Brazilian soil inconceivable.
Messi added: "[The squad] is hurt by the situation because we can't manage to win a game, and we know today was key for us.
"We know we have to win the next game to advance.
"We know we'll be playing for our lives.
"It would be crazy if we can't advance from the group stage, when basically three [teams] advance from each group. I have no doubt we'll do it."