Playing in his first official match at the historic Bombonera stadium, Lionel Messi almost opened the scoring midway through the first half, flashing his shot just wide of the post from outside the box after a superb run.
Benedetto shot straight at the keeper and Mascherano saw a long-range effort fly just over as Argentina tried desperately to find a victor.
Thursday's goalless draw against Peru leaves Lionel Messi and his beleaguered band of brothers in need of a positive result in the drowning altitude of Quito on Tuesday; failure to do so would make the seemingly impossible, a reality. The top four teams qualify automatically for Russian Federation, with the fifth-placed side facing Oceania champions New Zealand in a two-legged playoff in November for another place.
In Europe, defending champion Germany clinched a place with a 3-1 win in Northern Ireland, while England beat Slovenia 1-0 to secure its berth.More news: House Passes 'Pain Capable' Bill Banning Abortion After 20 Weeks
The final group game would see Argentina travel to Ecuador at Quito, more than 2800 metres above sea level, and these are conditions that they usually fare poorly in.
Eduardo Vargas netted his 35th career goal for his country in the 22nd minute, receiving in the centre of the box before side-footing past Ecuador keeper Maximo Banguera.
Alexis Sanchez was on hand just minutes later to score the victor from close range.More news: Embassy caused delay of Jong-nam's autopsy, court told
La Roja will wrap up their qualification campaign at Brazil, who have already qualified.
Meanwhile a late victor by Arsenal forward Alexis Sanchez saw Chile beat Ecuador 2-1 to move above Argentina, who find themselves in sixth place with one game to go.
Oscar Cardozo bundled in the equaliser for Paraguay in the 89th minute and then Tony Sanabria punished poor goalkeeping by David Ospina to poke in a second in injury time to clinch the win. The last time he did not score in three consecutive games was in the 2015 Copa America, when he had a goal in the opener but did not score again in the final five games of the competition. Trouble is only the first four teams in the table can qualify for the World Cup and Perù have just as much points in the table as Argentina (24) with the same goal difference as well.
The draw gives ninth-placed Bolivia 14 points from 17 matches.More news: Two killed in Pakistan shelling on LoC (Second Lead)
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