The S&P 500 and the Nasdaq composite hit all-time highs before paring gains as investors looked for fresh catalysts following centrist Emmanuel Macron's widely expected victory in the French presidential election.
Comcast and Amazon.com were the top drivers of the two indexes.
Currency markets were in sharp focus, with the euro hitting a six-month high against the dollar after Macron comfortably defeated far-right nationalist Marine Le Pen who had threatened to take France out of the European Union.
"The results came in as expected and the market had already factored that in," said Andre Bakhos, managing director at Janlyn Capital in Bernardsville, New Jersey.
"The market is trading in a careful and deliberate way looking for the next driving force, which I expect will cause a strong move in either way."
At 9:40 am ET (13:40 GMT), the Dow Jones Industrial Average was down 25.4 points, or 0.12 per cent, at 20,981.54.
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The S&P 500 was down 1.98 points, or 0.08 per cent, at 2,397.31, easing from an all-time high of 2,401.36.
The Nasdaq Composite was down 4.77 points, or 0.08 per cent, at 6,095.99, after a record high of 6,106.11.
Seven of the 11 major S&P sectors were higher, with consumer discretionary rising the most by 0.24 per cent. Materials were the biggest losers. Cleveland Federal Reserve President Loretta Mester said the central bank's goals were largely met and interest rate hikes were on track.
However, St. Louis Fed President James Bullard said the rise in demand for safe assets remained strong and there was no need to rush rate hikes.
Shares of Kate Spade rose 8.2 per cent to $18.36 after bigger rival Coach Inc said it would buy the company for $2.4 billion. Coach's shares rose 7.2 per cent.
Straight Path surged nearly 27 per cent to $204.86 after an unnamed telecommunications company raised its offer to buy the wireless spectrum holder for about $3.1 billion, trumping a bid by AT&T. Sources told Reuters that the bidder was Verizon.
Tyson Foods was the biggest S&P loser, down 4.7 per cent after the meat processor reported a slump in quarterly profit.
Declining issues outnumbered advancers on the NYSE by 1,352 to 1,183. On the Nasdaq, 1,255 issues fell and 1,040 advanced.
The S&P 500 index showed 33 52-week highs and one low, while the Nasdaq recorded 53 highs and 15 lows.