(CNN) -- Brazil need just three more points to clinch qualification for the 2010 World Cup after beating former South American Group leaders Paraguay on Wednesday, but Argentina's hopes suffered a big blow.
Brazil's match-winner Nilmar, left, celebrates his goal with Elano and Daniel Alves, right.
With four matches remaining, Brazil retained top spot with a 2-1 victory in Recife to lead second-placed Chile by a point, with Paraguay two further adrift on 24 and Argentina in fourth on 22.
The top four teams automatically qualify for next year's finals in South Africa, while the fifth-placed nation -- Ecuador at this stage -- face a play-off against the fourth-placed side from the CONCACAF region. Mexico hold that spot following Wednesday's matches, following a morale-boosting 2-1 win against bottom nation Trinidad and Tobago.
Brazil and Paraguay had been level on points at the top of the table of Wednesday's clash, and the visitors took the lead in the 25th minute when Salvador Cabanas's free-kick took a deflection off midfielder Elano and looped over Julio Cesar.
Elano's Manchester City team-mate Robinho made amends with a superb volleyed equalizer four minutes before half-time from Daniel Alves' right-wing cross.
The home side then went ahead four minutes after the interval with a scrappy goal as striker Nilmar scrambled the ball into the net after a fortuitous rebound off Paraguay's Julio Cesar Caceres when he tried to chest the ball down to Kaka.
"It was a match in which we had to be patient and persistent," Brazil coach Dunga said on FIFA.com.
"We had to try playing on the wings, at speed, changing sides. Everyone plays tight away from home and that makes it difficult to win. We need three more points to be sure (of qualifying)."
For Paraguay, who were four points clear at the top at the halfway stage, it was a second setback in a week after Saturday's 2-0 home defeat by Chile.
Diego Maradona's Argentina were unable to follow up last weekend's 1-0 win over Colombia, crashing 2-0 away to Ecuador at high altitude in Quito.
Carlos Tevez missed a first-half penalty before goals from Walter Ayovi and Pablo Palacios handed Maradona a second defeat in four qualifiers since taking charge.
"They didn't do anything in the first half," Maradona said on FIFA.com. "In the second half, they got a couple of rebounds and they scored two goals. If we had scored a goal, it would have finished the game off."
Ecuador coach Sixto Vizuete, whose side closed to within two points of the Argentines, said: "These three points are worth their weight in gold and we're satisfied because we beat great opponents."
Tevez was fouled by Ecuador goalkeeper Marcelo Elizaga just inside the penalty area in the 28th minute, but then saw his weak spot-kick saved and Lionel Messi fired the rebound over the bar to add to an earlier easy miss by the the Barcelona forward.
Left-back Ayovi equalized in the 72nd minute with a superb 25-meter strike, then substitute Palacios -- who had teed him up for that effort -- fired the winner with seven minutes left and Antonio Valencia struck the visitors' woodwork with a long-range shot.
Jean Bonsejour headed the opener just before halftime from Matias Fernandez's right-wing cross, Mark Gonzalez made it 2-0 with a free-kick in the 74th minute before Sanchez struck four minutes later.
Sanchez scored again just before the end, and midfielder Ignacio Garcia was sent off after clattering into him while he celebrated.
Diego Forlan put Uruguay 2-1 up in the 73rd minute, but Venezuela kept their hopes of a first World Cup finals appearance alive when Jose Manuel Rey scored from a trademark free-kick two minutes later.
Radamel Falcao Garcia netted the only goal in Medellin from close range in the 25th minute, scoring just his nation's seventh of the qualifiers as Peru crashed to an eighth successive defeat.