Cristiano Ronaldo scored on a powerful header in the 79th minute, sending Portugal to the European Championship semifinals with a 1-0 victory over the Czech Republic on Thursday.

Ronaldo hit the post twice, then finally delivered. He headed a cross by Joao Moutinho straight at the ground and up past the flailing hands of Czech goalkeeper Petr Cech.

This was Ronaldo's third goal in two games and it rewarded the Portuguese for the relentless pressure they applied all match.

"We had a lot of chances," said Ronaldo. "We had a great unity on the pitch and that is why we have reached our goal."

Portugal will play Spain or France in the semifinals in Donetsk, Ukraine, on Wednesday. It is one victory from its second European Championship final in eight years.

Ronaldo already provided some leadership and two goals to get past the Netherlands in group play, and his encore Thursday was huge.

His goal finally punished the tactics of the Czechs, who had parked most of their players in front of Cech for much of the game.

"The Czechs didn't have a single chance," Ronaldo said.

The strategy worked for a while. In first-half injury time, Ronaldo deadened a cross from Raul Meireles on his chest, turned and with two touches set up a right-foot shot that had Cech beaten before it crashed against the near post.

In the 49th, Ronaldo again clipped the post on a free kick from 25 yards out.

By then, Ronaldo had hit the post four times in two games. When he finally scored and was mobbed by teammates, he went over to the TV camera with a beaming smile and offered a victory kiss.

"We have suffered," Portugal forward Nani said. "But we always wanted to win and that's what we showed. We were superior, then we scored and we really deserved this result."