New Zealand skipper Stephen Fleming revealed his side were not at their best against the USA in the Champions Trophy, despite a 210-run victory.
"The occasion put pressure on us," Fleming said afterwards.
"It was a tough one to play because you always have the worst-case scenario - having to come in here and explain why you have lost.
"We had an anxious start with bat and ball. But I think the guys were tight and in the end we kept on top of the job."
The Black Caps made 347-4 from their 50 overs.
After a slow start, big partnerships between Nathan Astle and Scott Styris and Astle and Craig McMillan made the USA's inexperienced attack pay for some slack bowling.
"They were in the game at certain times, but if you apply enough pressure you know they are likely to crack much more quickly than teams who have had more exposure at this level," said Fleming.
Man of the Match Astle, who top scored with an unbeaten 145, was delighted with his big knock.
Astle's score was his highest in a one-day international
"It was good to get runs and I'm looking forward to the next game against Australia," he said.
"We didn't know what were were up against at The Oval. But after getting used to the USA bowlers we managed to hit some sixes towards the end."
Despite New Zealand's attack restricting the Americans to 137, it took their bowlers more than 42 overs to finish the job despite Jacob Oram picking up five wickets.
"Once we got on top it proved hard to keep that lift up," he added.
"But when you're out there in that situation there's no reason why you shouldn't be motivated."