Argentina, shooting for a first Olympic women's hockey gold, were held to a two-all draw by the United States in the rain while former champions Australia scraped past South Korea 5-4 in first round matches.

World number two Argentina, the in-form team after winning this year's Champions Trophy, were 2-0 up inside 11 minutes thanks to Carla Rebecchi goals.

But the Athens bronze medallists were held in their pool B game despite dominating it, forcing three times more penalty corners and as many goal attempts.

"Our accuracy was affected by the rain while converting penalty corners," Argentina coach Gabriel Minadeo said through an interpreter.

The US pulled one back in the first half through an opportunistic goal by Keli Smith arising from a penalty corner while Angela Loy scored the equaliser six minutes to the finish.

They were reduced to 10 players for nearly 20 minutes in the second half due to yellow card suspensions.

"We are totally satisfied but in saying that we knew that we had to bring our best game," US coach Lee Bodimeade said.

Asian Games champions China in pool A garnered maximum points against Spain after Japan beat New Zealand 2-1 in pool B.

Former champions Australia meanwhile fought back from a three-goal deficit in their pool A match to score maximum points.

Korea went up 4-1 through strikes from Kim Darae, Gim Sung Hee and Park Mi Hyun in the space of seven minutes.

Stretched by not rattled, Australia, who won consecutive titles in 1996 and 2000, scored through captain Nicole Hudson. Shelly Liddlelow reduced the margin and Sarah Young equalised.

Five minutes to close, Casey Eastham scored the winner.

Defending champions Germany meet Britain and top-ranked the Netherlands will take on South Africa in the remaining first round matches later today.