Spain are among the favourites to lift the trophy and returned to top form with an impressive 3-0 victory over Austria in the Round of 32 after a slow start to the tournament.
Garcia acknowledged the quality of the European champions but said Belgium have the attacking strength and confidence to compete with them.
"We know we are playing one of the favourites," Garcia said. "Spain are probably the best team when it comes to ball possession and they have played in the same recognisable way for 15 or 20 years.
"But we have a great team. We are one of the highest-scoring teams at the World Cup and we are facing the team with the highest expected goals. We believe we can do it."
Belgium have scored 13 goals so far at the tournament, making them the third-highest scorers behind France with 16 and Argentina with 14.
Experienced striker Romelu Lukaku admitted Belgium will have to produce their best performance of the tournament if they are to reach the semi-finals.
"If you get this far, you don't play just to go home," Lukaku said.
"Spain are an excellent team. They look for the third man, they have speed on the wings and they create depth. But we are well prepared and we have qualities that can make life difficult for them."
The 33-year-old also revealed that his role in the team was discussed with Garcia before the tournament and said his priority is helping Belgium in every way possible.
"It's about the team," Lukaku said. "I try to help on the pitch and off the pitch. At this stage of my career, you have to play with your head as well."
Belgium are also expecting a difficult atmosphere at Los Angeles Stadium after knocking hosts the United States out of the competition with a convincing 4-1 victory in Seattle.
Garcia, however, said his players have already shown they can handle hostile crowds.
"We just beat the US in a stadium where everyone was against us," he said.
"It's not the crowd that scores the goals. We will focus on what we can do. We have enough on our plate with Spain, who are a wonderful footballing team.
"Even if we are the underdogs, we will do everything we can to give them a run for their money."
