A late winner by Arsenal forward Alexis Sanchez helped Chile beat Ecuador 2-1 to leapfrog Argentina in the qualifying table into fifth place.
Only the top four teams in the South America group are guaranteed to be on their way to Russia next year, while the team that finish fifth will play New Zealand in a two-legged play-off in November.
A win for Argentina in Quito, which lies at nearly 2,900 metres above sea level, may yet throw them a lifeline but they will need other results to go their way if they are to secure an automatic qualifying berth.
Sky Sports reports that in the night’s other game, Colombia missed out on the opportunity to seal their place at next year’s finals after they were beaten 2-1 at home by Paraguay, who kept alive their slim hopes of making it to Russia.
Monaco striker Radamel Falcao – who has also had loan spells in the Premier League with Manchester United and Chelsea – scored the opening goal for Colombia after 70 minutes.
But goals from Oscar Cardozo a minute from time and a stoppage-time winner from Antonio Sanabria secured the points for Paraguay.