"We haven't lost yet, of course you can beat anyone on a good day," said the 30-year-old keeper, who helped Chelsea lift the UEFA Champions League trophy last month. "We definitely have a chance to advance. It's sport and anything can happen," he added.
The Czechs advanced as surprise Group A winners along with second-placed Greece, while Portugal came second in Group B behind Germany after beating Denmark and, in the last game on Sunday, the Netherlands.
"They are among the world's top ten teams. It's a team full of personalities and outstanding players, and they play very well. Against the Netherlands on Sunday, they were excellent up front," said Cech. "They also have enough experienced players. The team has matured and it's really strong," he added.
Cech also said he reckoned Cristiano Ronaldo, who scored twice in the 2-1 victory against the Netherlands, was one of the world's top two players along with Lionel Messi, diplomatically declining to say which of them was better. "He has a powerful shot, he can shoot with his left or right, he can score from any place, he's great at heading," Cech said.
The Czechs, playing their fifth straight EURO tournament, eliminated Portugal in the 1996 quarter-final on their way to the final but lost to the same rival in the group stage of the 2008 tournament. "I hope the result will be different now than in 2008," said Cech, who has unhappy memories of the 3-1 defeat as he was in goal.
Kadlec hopes for '96 repeat
His side prefer to recall 1996 when Karel Poborsky memorably chipped the ball over Portugal's keeper to hand his side a 1-0 win. "We wouldn't grumble if it happened again," said defender Michal Kadlec, whose father Miroslav was the 1996 team captain.
"When we have started like this, we don't want to end up losing in the quarter-final," added Kadlec, whose stunning clearance off the line in the closing minutes of the 1-0 win over Poland saved the Czechs from bowing out of the competition.
Cech said he hoped for at least a repeat of the 2004 edition, hosted by Portugal, where the flair-filled side, with him in goal, reached the semi-finals before losing to eventual winners Greece. "We have a chance to emulate that success from Portugal. It's enough to win one game, and I believe it will be a good game for us," said Cech.