Mission Hills China:A storming finish from young hotshot Rory McIlroy propelled hotly fancied Ireland into a three-shot lead over Argentina as they ended the first day of the World Cup in style on Thursday.
Twenty-year-old McIlroy, who finished second on the European money list, sank a 20-foot putt for eagle at the par-five 15th and missed repeating the feat on the par-four 16th by a whisker, settling for a birdie.
The world number ten then sank a putt for birdie on the 17th before partner Graeme McDowell sank a 12-footer on the last for another birdie to take Ireland to a 14-under-par total of 58, just one off the World Cup record for fourballs.
Japan were a shot adrift of Argentina at ten under, with Italy, Canada, South Korea and defending champions Sweden two shots further back on eight under after the opening fourball round in this 5.5-million-tournament.
Defending champions Sweden, who include Henrik Stenson and Robert Karlsson, hit six birdies in their opening nine holes on the bunker-strewn Olazabal Course but failed to maintain their momentum.
England's Ian Poulter and Ross Fisher finished on six under while last year's runners-up Spain ended on a disappointing three under, with world number eight Sergio Garcia struggling to make an impact.
A Rafa Echenique eagle on the 15th helped take Argentina, also featuring Tano Goya, to their total of 11 under par.
"We were pretty solid today. We hit a lot of greens, a lot of fairways today, as well. So I think we make a really good combination," said Goya.
"The times he was in trouble, I was there and the times I was in trouble, he was there. That's the good thing about the fourball/best ball; that it's important for one to make it really good."
Japan's Ryuji Imada said: "I think we gelled really well. The holes that I struggled, he made pars or birdied and vice versa, and we got it to 10 under," referring to team-mate Hiroyuki Fujita.
Italy's Italy Edoardo Molinari, playing with his brother Francesco, said he felt confident after his win at the Dunlop Phoenix tournament in Japan on Sunday, in which he beat Karlsson in a play-off.
"Winning in Japan was a great boost for the confidence because it was a great field last week, almost like a European Tour event," he said.
The Omega Mission Hills World Cup, taking place near Shenzhen in southern China, is a 72-hole event with each team comprising two players.
The first and third days are fourball, in which four balls are used and the player with the fewest shots takes the hole for their team. The second and final days involve foursomes play, where the teams compete using only one ball per pair.