Defending champions Sweden raced into second place behind Ireland’s powerful pairing of Rory McIlroy and Graeme McDowell.
Ireland, taking a three-shot lead into the foursomes after a blistering fourballs first round, sank five birdies and an eagle to lead by three strokes at 18 under after 36 holes at Mission Hills.
Sweden, featuring world number seven Henrik Stenson and 2008 European Order of Merit winner Robert Karlsson, moved to 15 under following the only blemish-free round of the day, which included seven birdies.
Sweden followed up their opening day 64 with a 65. Their seven birdies included a 20-foot Stenson putt at the par-three 17th.
Karlsson said: “We played well yesterday (Thursday). Didn’t really put the score together, but I definitely felt like we played a lot better yesterday than we did last year.
“So at the end of the day it was a little bit frustrating with a 64, but I knew that the game was there to put a good score together today, and we did, so that’s very, very encouraging.”
The Italian team, made up of the Molinari brothers, Francesco and Edoardo, were on 14 under with Japan a further three shots back and Wales and Venezuela on 10 under.
McIlroy said Ireland were satisfied after they ended the day with a three-shot lead, the same margin as at the start of the round, even though they were unable to match their first-round performance.
“It was a good day. You know this format is, foursomes is a little trickier than the fourball. You have to, if you hit it in trouble, you’re relying on your partner to sort of get you out, where you’re taking responsibility for your own actions a bit more whenever you’re playing in the fourball.”
“I think we probably would have taken 68 on the first tee. We had a go today to get a bit lower than that but we played very solidly. Apart from the couple of mistakes on the back nine, we could have got a really good score in there,” he added.
“But I think in the end we showed really good character to come back with two birdies on 16 and 17 after the double on 15. So it was a good day.”
McDowell and McIlroy, who finished second on the European money list, were off to a good start after two birdies and an eagle on the front nine, giving them a five- shot lead at the turn.
Ireland dropped their first shot of the tournament on the par-five 11th. A double- bogey seven at the par-five 15th after McDowell found the water threatened to cost them dear.
But they struck birdies on the 16th and 17th to leave themselves with a three-shot cushion going into Saturday’s fourballs.
Argentina, in second place after 18 holes, fell away sharply, with two double- bogeys and another bogey in their last seven holes, leaving them in joint 11th position.
England, with Ian Poulter and Ross Fisher, were nine under after 36 holes on the bunker-strewn Olazabal Course.
And the Spanish challenge, led by Sergio Garcia, ranked eighth, continued to falter as they ended the day on four under, effectively out of contention.
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.