Scotland must beat England to have any hope of progressing to the knockout stages of the World Cup after suffering an agonising Pool B defeat to Argentina in Wellington.
Chris Paterson and Ruaridh Jackson kicked a penalty apiece as Scotland took a 6-3 half-time lead after Felipe Contepomi had put Argentina in front.
Contepomi levelled with a 63rd-minute penalty before Jackson stroked over a drop goal two minutes later and his replacement Dan Parks extended Scotland's lead eight minutes from time with another drop goal.
That pushed Andy Robinson's men six points clear, but Argentina won the ball from the restart and spread the ball wide to the right and Lucas Gonzalez Amorosino touched down.
Contepomi kicked the subsequent conversion and Parks missed a drop-goal attempt one minute from time as Scotland suffered defeat for the first time in five matches.
Scotland claimed a losing bonus point and are now level on 10 points with Argentina, who play Georgia next Sunday.
Robinson's men must win next Saturday's clash with England at Eden Park in Auckland to have any hope of preserving their record of reaching the knockout stages at every World Cup.
But Argentina will now be fancied to advance if they can claim a four-try bonus point against Georgia.
History suggested it was always going to be tight - just two of the previous 12 Test meetings between the sides had been settled by a score in double figures.
And a dour contest was played in torrential rain, exacerbating the number of errors.
Scotland scrum-half Rory Lawson continued as skipper following the 15-6 win over Georgia, with tournament captain Alastair Kellock left out of the matchday 22.
Wet conditions did not stop Scotland looking to move the ball, with Jackson pulling the strings.
Paterson pushed a penalty wide after eight minutes, before Martin Rodriguez was off-target with a drop goal at the other end.
Contepomi missed a long-range attempt before he was successful with an effort from in front of the posts to hand his side the lead after 19 minutes.
Rodriguez missed a long-range penalty attempt before Scotland sought to move their opponents around.
Nick De Luca and Max Evans looked dangerous with a couple of bursts before John Barclay took the ball into contact wide on the left when Lamont was outside him.
Sean Lamont and then Alastair Strokosch turned over the ball in promising positions for Scotland.
Strokosch lost the ball forward, but Argentina prop Rodrigo Roncero was penalised at the subsequent scrum and Paterson levelled matters after 36 minutes.
Roncero was replaced at the next stoppage with Martin Scelzo introduced.
It was the second Argentina substitution after Genaro Fessia had earlier replaced key number eight Juan Martin Fernandez Lobbe, who appeared have a knee problem.
Jackson assumed the kicking duties for a 45-metre penalty after Argentina failed to release and he put Scotland in front for the first time one minute before the interval.
The rain continued to teem down and the match remained tight and cagey early in the second period.
An Evans chip and chase almost ignited matters, but Barclay lost the ball in support and Argentina scrambled clear.
Jackson kicked the ball out on the full and Argentina knocked on from the subsequent line-out as the errors mounted.
Paterson missed a drop-goal attempt from inside the Argentina 22 after Scotland had made inroads only to encounter stubborn defence.
Contepomi missed a penalty attempt before Scotland tighthead Geoff Cross was again penalised at the scrum for collapsing the front row. Contepomi levelled the scores, but Jackson restored Scotland's lead two minutes later with a drop goal.
Contepomi hit the post with another penalty attempt to reprieve Scotland, who then pushed deep into opposition territory after Parks replaced Jackson.
Dougie Hall, on at hooker for Ross Ford, found Strokosch at the back of the line-out and Scotland attempted to rumble their way to the line before Mike Blair, on for Lawson, found Parks who drilled over a drop goal.
It pushed Scotland six points clear, but from the restart Argentina won the ball, spread it wide and Gonzalez Amorosino evaded Paterson's attempted tackle and the covering Lamont to score.
Contepomi kicked the conversion to hand the Pumas a one-point lead.
Gonzalez Amorosino almost turned from hero to villain as he fumbled Parks' kick on his own line.
Scotland's forwards won the line-out and moved into position for a drop-goal attempt.
Under pressure, Parks had to make space for a left-foot shot at goal and missed and Scotland's chance was gone as the Pumas triumphed.