Buenos Aires  - The South American qualifiers for the 2010 World Cup in South Africa reach their half-way mark this weekend, and there is great unrest among regional giants Brazil and Argentina over bad results and generally poor form.

Paraguay lead the table with 17 points in eight games, and Brazil, Argentina and Chile follow with 13 points, while Uruguay is on 12.

"The qualifiers are always difficult, and you no longer win just with names. World football is very balanced," warned veteran Argentine defender Javier Zanetti.

On Saturday, Paraguay are set to visit Colombia, while Argentina - which has not won a game in the last five rounds of the qualifiers - host Uruguay. Peru play away against Bolivia at high altitude in La Paz.

On Sunday, Brazil will visit Venezuela and Chile play an up-and- coming Ecuador.

In South America's 10-team World Cup qualifiers, each side plays each of the other nine teams at home and away. The top four win a place in the World Cup. The fifth-ranking team also has a chance to advance if it wins a playoff against a representative of the North, Central American and Caribbean region.

In Brazil's latest game - an embarrassing goalless draw against lowly, 10-man Bolivia in Rio de Janeiro - fans shouted insults at coach Carlos Dunga, calling him "burro" or "donkey," and screaming "adeus" or "goodbye" as they demanded his exit.

As had happened weeks earlier against Argentina in Belo Horizonte, the home crowd hurt the Brazilian players by cheering for their rivals.

One commentator called that performance "possibly (Brazil's) worst game in many years."

Booing and strong criticism are not new for Dunga's team in the qualifiers. However, Brazilian Football Confederation officials have backed the coach, and Dunga himself has said he will not resign.

Their rival on Sunday, Venezuela, is the only country in the region where football is not the most popular sport. It has lost its last three games in the qualifiers, and coach Cesar Farias is under fire to perform.

And yet Venezuela have already beaten Brazil this year, 2-0 at a friendly played in Boston in June, which was their first-ever triumph against the winner of a record five editions of the World Cup.

"This Brazil is going to be different from the one that played in Boston. I'm sure they will be more cautious now. But we have to keep the attitude that gave us the win that day," Venezuelan striker Giancarlo Maldonado told the media.

Brazilian star Kaka and several of his team-mates made it clear that they are not seeking revenge for the recent defeat against Venezuela.

"Our goal is to get three points. It is that which is important, not scoring many goals," Kaka told Deutsche Presse-Agentur dpa.

As things stand, however, anything other than a resounding win in San Cristobal is likely to cost Brazil dearly on Wednesday, when Dunga's men host Colombia in Rio de Janeiro.

Argentina are not doing much better. Of their last five games in the qualifiers, they lost away in Colombia and then drew against Ecuador, Brazil, Paraguay and Peru. Fans expect a lot more from a team built around the talent of Lionel Messi, and they are growing restless over the poor performance.

"Even if he loses, (coach Alfio) Basile is not leaving," insisted Argentine Football Federation president Julio Grondona.

"We all want Argentina to finish in the highest spot, and we hope we can manage it," said right-back Javier Zanetti.

Sailing in much calmer waters, the qualifiers' leader Paraguay is playing Colombia without star striker Roque Santa Cruz, who is injured. And the Colombian side will feature new coach Eduardo Lara, following the sacking of Jorge Luis Pinto.

Chile will try and keep up their hopes of qualifying, when they visit Ecuador. While the Ecuadorians lost their first three games en route to South Africa, they haven't dropped a game since and it looks like their recovery is for real.

The qualifiers will continue Tuesday and Wednesday. Tuesday will feature Bolivia-Uruguay, with Paraguay-Peru, Chile-Argentina, Venezuela-Ecuador and Brazil-Colombia playing a day later.

A break in the qualifying round will follow, with the next games to be played late March. (dpa)