"This is a really difficult competition," said Ronaldo, who is playing in the South American World Cup qualifiers for the first time.

"Our team has always had difficulty qualifying but we have to get over this -- if we don't, we won't go to the World Cup," he told reporters on Tuesday, a day ahead of Brazil's match against Paraguay.

"All the games are difficult but we have to get over the other problems -- the travelling, the tiredness, the lack of understanding on the field."

Ronaldo played for Real Madrid at the weekend, arrived in Asuncion on Monday and will be back in Spain in time for the following weekend.

"For the qualifiers, everyone has to make a sacrifice. All the players are aware of this. The players who are in Europe have to travel a long way and, at the end, we have to get a result.

Brazil are third in the South American qualifying group with eight points from their first four games, one less than Paraguay who lead the group.

Ronaldo added that other teams tried harder against Brazil.

"To play against the five-times world champions is an incentive for anyone," he said.

Ronaldo was included Brazil's 1994 World Cup squad as a 17-year-old but did not play in the qualifiers. Brazil, as 1994 champions, did not have to play in the 1998 qualifiers and Ronaldo missed the 2002 qualifiers because of his knee injuries.