An 11-under 61 on the first day has taken the United States to the top of the OMEGA Mission Hills World Cup leaderboard in China as the Australian team of Nathan Green and Nick O&aposHern find themselves five strokes off the pace. American team-member Boo Weekley, though, has admitted he found it difficult to hold back the tears when he received the call to represent the US. Speaking after an impressive opening round, the 34-year-old and playing partner Heath Slocum carded their 61 on Thursday to take a one-stroke lead over the German team, consisting of Alex Cejka and Martin Kaymer. The United States had received some criticism for not sending higher-ranked players to the tournament, with Weekley 43rd in the world rankings and Slocum 70th. But the pair combined to record an impressive seven birdies and two eagles to put themselves in early contention for a 24th World Cup success. Weekley expressed his delight at being able to represent his country at the Mission Hills Golf Club. “When I found out I was in I nearly cried because just to be able to come over and represent the United States is a plus for me,” he said. “Also, to be able to call one of my good friends, Heath Slocum, up and ask him to come and play with me is even better.” “I was teary-eyed because it was awesome.” The Americans are also two strokes ahead of six nations – Finland, Wales, Scotland, South Africa, Thailand and England – at nine-under as France and Austria find themselves a further stroke adrift. Korea, Italy, The Netherlands, Denmark, India, Argentina and host nation China are all at seven-under on the leaderboard after carding 65s on the opening day, as Australia finds itself one stroke further back in a tie for 18th as O&aposHern and Green posted a six-under 66. The Aussies are still one-stroke ahead of New Zealand pair Richard Lee and Stephen Scahill, though. First round of the Omega Mission Hills World Cup: -11 United States 61 -10 Germany 62 -9 Finland 63, Wales 63, Scotland 63, South Africa 63, Thailand 63, England 63 -8 France 64, Austria 64 -7 Korea 65, Italy 65, Netherlands 65, Denmark 65, India 65, Argentina 65, China 65 -6 Paraguay 66, Sweden 66, Canada 66, Ireland 66, Australia 66 -5 Philippines 67, New Zealand 67, Spain 67, Japan 67 -4 Colombia 68, Puerto Rico 68