At 8:52 a.m. ET, Dow e-minis were down 28 points, or 0.11 percent.
The biggest drag on the S&P 500 was Booking Holdings (BKNG.O), which fell 5 percent after it forecast third-quarter profit below expectations.
Energy weighs on the S&P 500 on Thursday.
Shares of Apple rose 1 percent, while those of Amazon were up 0.8 percent and Microsoft 0.4 percent.
The Toronto Stock Exchange's S&P/TSX fell 90.47 points, or 0.55 per cent, to 16,326.51, led lower by the health care, consumer staples and utilities sectors.
The S&P 500 opened lower by 13.94 points, or 0.49 per cent, at 2,839.64.
"When we see the earnings growth in 2018, the multiples are reasonable at that record level", said Art Hogan, chief market strategist at B. Riley FBR in NY.
The S&P 500 index slipped after coming within spitting distance of a record high following a four-day rise.
Microchip Technology shares fell 10.9 per cent after a disappointing second-quarter revenue forecast.
The number of Americans filing for unemployment benefits unexpectedly fell last week, suggesting that a strong economy was helping the labor market counter ongoing trade tensions.
Seven of the 11 major S&P sectors were higher, with the materials sector leading the gains as aluminum prices rose. Shares of Apple rose 0.8 per cent, while those of Amazon were up 0.6 per cent.
Rite Aid fell 10.9 percent after the drug store chain and USA grocer Albertsons Cos agreed to terminate their merger agreement.
The Nasdaq Composite Index increased 4.66 points, or 0.06 per cent, to 7,888.33.
Meanwhile, in the US, the dollar strengthened, gaining 0.68%.
Meanwhile, concerns over escalating trade conflict between the USA and China weighed on the trade-sensitive S&P 500 Industrials Index, which ended up losing 0.57% on the day.
Declining issues outnumbered advancing ones on the NYSE by a 1.04-to-1 ratio; on Nasdaq, a 1.10-to-1 ratio favoured advancers. That compares with the 6.3 billion daily average for the past 20 trading days, according to Thomson Reuters data.