* March U.S. private sector job additions beat estimates
* Record highs for Amazon, Microsoft and Apple
* Indexes up: Dow 0.59 pct, S&P 0.52 pct, Nasdaq 0.4 pct (Updates to late afternoon, adds commentary, changes byline)
By Sinead Carew
April 5 (Reuters) - U.S. stocks rose on Wednesday in a broad-based rally, spurred by private-sector employment data that blew past expectations and boosted investors' confidence in the strength of the economy.
The S&P was on track for its biggest one-day percentage gain in six sessions after data showed that U.S. companies added 263,000 workers in March, the most since December 2014 and well above economists' expectations of 187,000.
The report by payrolls processor ADP comes ahead of Friday's nonfarm payrolls data that includes hiring in both the public and private sectors.
"The real driver of this leg up heading into earnings season is all about economic data," said Peter Kenny, senior market strategist at Global Markets Advisory Group, in New York, adding that investors see improving economic data as an indicator that "equity prices will likely continue to move higher as a result of improving earnings."
All 11 major S&P 500 sectors were up, with the information technology sector the biggest driver. The Nasdaq hit an all-time high, buoyed by Amazon. Microsoft and Apple.
The S&P pared its gains after the Federal Reserve released the minutes from its most recent meeting but this was investor profit-taking rather than anything worrying in the minutes, according to Dennis Dick, head of markets structure, proprietary trader at Bright Trading LLC in Las Vegas.
"People are so scared to be not participating now so every time we pull back a little bit, money managers come in with big bucks," said Dick, adding that investors had cash on the sidelines. "You're starting to see almost panic buying."
At 2:35 PM EDT (1835 GMT), the Dow Jones Industrial Average was up 122.11 points, or 0.59 percent, to 20,811.35, the S&P 500 had gained 12.31 points, or 0.52 percent, to 2,372.47 and the Nasdaq Composite had added 24.02 points, or 0.41 percent, to 5,922.63.
The ADP report drew some money back into the market after a period of range-bound trading as some investors have hesitated over worries about President Donald Trump's ability to deliver on his policy plans after recent setbacks in Congress.
However, investors are cautiously awaiting a meeting this week between Trump and Chinese President Xi Jinping which Trump expects to be a "very difficult one."
Market valuations may also be tested when the earnings season starts next week, according to Myles Clouston, senior director at Nasdaq Advisory Services in New York.
"Valuations from a historical standpoint are in the high end but as long as earnings growth and GDP continue to do well, there is argument that they are justified," said Clouston.
Panera Bread jumped 14 percent to $312.60 after JAB Holdings said it would buy the bakery chain for $7.16 billion.
Advancing issues outnumbered declining ones on the NYSE by a 1.54-to-1 ratio; on Nasdaq, a 1.03-to-1 ratio favored advancers.
The S&P 500 posted 38 new 52-week highs and four new lows; the Nasdaq Composite recorded 71 new highs and 43 new lows. (Additional reporting by Rodrigo Campos in New York, Yashaswini Swamynathan in Bengaluru; Editing by Savio D'Souza and James Dalgleish)