Villa Carlos Paz - World champion Sebastien Ogier saw his chances of winning the Rally of Argentina go up in smoke after he failed to finish Friday's second special stage with a technical problem.
"Everything went fine but after 10km, we started losing power, like we were running on just three cylinders," the French driver told journalists.
"That's sport, there's an element of luck. This time, it wasn't for us."
The Frenchman's Volkswagen Polo stopped 46km into the stage, with a team spokesperson saying it wasn't an accident.
"The team will have to determine the source of the problem and if it's an electronic failure or a breakdown in the fuel supply, I will most likely be able to continue," added Ogier who has won all three of the championship rallies so far this year.
"If it's engine-based, I'll probably have to head home."
If the Polo is repaired, Ogier will be able to restart on Saturday, but with a 25-minute penalty, which would rule out any chance of him finishing high up the standings save for an enormous surprise.
Britain's Kris Meeke, at the wheel of a Citroen DS3, took full advantage to finish top of the standings at the halfway mark.
He has a 1:08.8 lead over team-mate Mats Ostberg with Volkswagen's Jari-Matti Latvala in third at 1:23.5 off the pace.
Rally of Argentina standings after Friday's stages:
Meeke-Paul Nagle (GBR-IRL/Citron DS3) 1h44:47.8, 2. Mads Ostberg-Jonas
Andersson (NOR-SWE/Citron DS3) at 1:08.8, 3. Jari-Matti Latvala-Mikka
Anttila (FIN/Volkswagen Polo-R) 1:23.5, 4. Dani Sordo-Marc Marti
(ESP/Hyundai i20) 1:54.2, 5. Elfyn Evans-Daniel Barritt (GBR/ Ford
Fiesta RS) 1:59.7, 6. Martin Prokop-Jan Tomanek (CZE/Ford Fiesta RS)
3.27.4, 7. Thierry Neuville-Nicolas Gilsoul (BEL/Hyundai i20) 5.06.2
Note: Sebastien Ogier-Julien Ingrassia (FRA/Volkswagen Polo-R), DNF SS2
Meeke 2 (SS2, SS4), Ogier 1 (SS1), Latvala 1 (SS3), Sordo (SS6)