Arch-rivals Brazil and Argentina drew 0-0 in a World Cup qualifier on Wednesday but moved closer to leaders Paraguay who lost 4-2 in Bolivia.
Ecuador and Colombia also played out a goalless draw in Quito, leaving the Colombians as the only unbeaten team after six matches in the 10-team group.
Brazil coach Dunga, whose side lost 2-0 in Paraguay on Sunday, was jeered and insulted by a 52,000 crowd at Belo Horizonte's Mineirao stadium as Argentina dominated the second half.
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Paraguay still lead the standings with 13 points but are only two clear of Argentina. Colombia are third with 10, followed by Brazil (9), Uruguay (8), Venezuela and Chile (7) and Ecuador (5).
Venezuela meet Chile in Puerto La Cruz on Thursday. The top four teams qualify directly for South Africa in 2010 and the fifth plays off against the fourth team from the CONCACAF region.
Dunga, whose team were again disorganised in midfield, said it is too early to contemplate the possibility of Brazil missing out on a World Cup for the first time.
"The qualifiers don't finish today," he said. "There are another 12 rounds of games to go."
Brazil edged the first half, Julio Baptista producing an outstanding close-range save from Roberto Abbondanzieri.
But Argentina, beaten by three-goal margins in their last three meetings with Brazil, dominated the second.
Julio Cruz and substitute Sergio Aguero missed excellent chances while Lionel Messi was foiled by Julio Cesar and fired wide from the rebound in stoppage-time.
Paraguay, facing high altitude and a shocking pitch in La Paz, finally came unstuck as they lost for the first time in the group against a team who started the day in last place.
Joaquin Botero and Ronald Garcia put previously winless Bolivia 2-0 up in 25 minutes.
In the second half, Botero and Marcelo Martins were on target for the hosts while Roque Santa Cruz and Nelson Haedo Valdez replied for Paraguay.
In Quito, Ecuadorean President Rafael Correa decided to show support for his team by staying away.
"I'm not going to watch the game at the stadium, because I believe I bring bad luck to football matches," said Correa, who last year watched Ecuador suffer their first home defeat for six years, at the hands of Venezuela.
Ecuador had slightly the better of the match and should have won when Luis Bolanos fired over the crossbar with the goal at his mercy near the end.