(Close): Most US markets fell in early trade, with energy shares continuing to fall as oil prices remained under pressure.
The tech-rich Nasdaq rose 18.34, or 0.37%, to 4,924.70, a 15-year high.
The Nasdaq rallied as online travel site Priceline gained 8.5% after reporting a 20% rise in quarterly earnings and announcing plans to buy back up to $3bn of shares.
The S&P 500 index dropped 2.23 points to 2,097.45.
Walmart shares fell 3.2% after the world's largest retailer cut its sales forecast for the coming year. It is now predicting sales growth of 1-2%, compared with an earlier forecast of 2-4%.
Walmart also announced it would spend $1bn on pay and training for its workers, which means that its hourly paid full-time and part-time workers will earn at least $9 an hour.