A point against Portugal will guarantee Mexico a place in the last 16 but defeat could spell the end of their tournament.

If Angola beat Iran and Mexico lose, the Africans and North Americans will be divided only by goal difference.

"We want to win the next match, I think if you get there thinking of only getting a point you might lose," Mendez told reporters on Monday.

"In this situation, anything can happen and you must be careful."

Mendez's teammate, midfielder Pavel Pardo, agreed that Mexico had to try to beat the Portuguese.

"We must win and we must qualify and that's all that is on our minds," Pardo said.

"Mathematics, whether we finish first or second, or who we might play next, does not concern us. It's all about winning."

Mexico beat Iran 3-1 in their opening match but were held scoreless by Angola, giving the Africans their first point on their debut at a World Cup.

Portugal have already reached the second phase after two wins while Iran will be heading home after two defeats.