Nasdaq hit all-time highs of 9,003, before paring gains to trade up 0.5 percent at 8,995 by 12:40 p.m. The technology sector has been the best performer among US stocks this year, lifting the Nasdaq index by more than 47 percent.
Wall Street’s S&P500 index, which measures the value of the 500 largest corporations by market capitalisation listed on the New York Stock Exchange or Nasdaq, was up 0.3 percent at 3,232 after hitting a record high of 3,235 earlier in the day.
The Dow Jones Industrial Average was up 0.2 percent at 28,567, after an intraday high of 28,596 that fell short of a previous record high of 28,609.
Wall Street has had one of its biggest and most prolonged bull runs this year on optimism over the imminent China deal as well as runaway jobs growth and other strong US economic data.
The Nasdaq has had 52 record highs in 2019 - averaging one every week - while the S&P500 witnessed 15 new peaks.