Lionel Messi scored on his return from international retirement as Argentina beat Uruguay 1-0 to go top of the South American World Cup qualifying group.
The Barcelona forward decided to stop playing for his country in June, but reversed the decision two months later.
Brazil remain in fifth place, outside the automatic qualification spots, despite their 3-0 win over Ecuador.
Manchester City’s summer signing Gabriel Jesus, 19, scored twice on his debut. with Neymar netting the opener.
Brazil have never failed to qualify for a World Cup and are only two points behind Argentina with more than half of the qualifying campaign to go.
A top-four finish would secure automatic qualification for Russia 2018, with fifth place securing a two-legged play-off with a team from Oceania – either New Zealand, New Caledonia, Fiji, Papua New Guinea, Solomon Islands and Tahiti.