* U.S. stocks on track for best performance since 2013
* Trump targets Amazon in call for postal service to hike prices
* Goldman warns of profit hit due to new tax law
* Indexes down: Dow 0.06 pct, S&P 0.06 pct, Nasdaq 0.16 pct (Updates to early afternoon)
Dec 29 (Reuters) - Losses in technology and financial stocks weighed on Wall Street on the last trading day of 2017, in what has been a banner year for U.S. shares.
Major indexes hit a series of record highs in 2017, riding on strong economic growth, solid corporate earnings and low interest rates.
The benchmark S&P 500 has surged 20 percent this year, the blue-chip Dow more than 25 percent and tech-heavy Nasdaq about 29 percent, setting them up for their best performances since 2013.
The market has also shown surprising strength despite tensions in North Korea and political upheavals in Washington. The S&P has closed below 1 percent only four times this year.
"By all accounts 2017 has been a great year for the market," said Arian Vojdani, investment strategist at MV Financial in Bethesda, Maryland.
"It is rich (in valuation) as of now and if prices and earnings continue to converge, I wouldn't be concerned."
Among sectors, the technology index has been the best performer, rising about 37 percent and outpacing gains in the broader S&P index.
Telecom services and energy are the only two sectors to end the year in the red.
The rally is widely expected to extend into 2018, boosted by gains from a new law that lowers the tax burden on U.S. corporations.
At 12:19 p.m. ET (1719 GMT), the Dow Jones Industrial Average was down 14.16 points, or 0.06 percent, at 24,823.35 and the S&P 500 was down 1.79 points, or 0.06 percent, at 2,685.75.
The Nasdaq Composite was down 10.92 points, or 0.16 percent, at 6,939.24.
Apple declined 0.52 percent after issuing a rare apology for slowing older iPhones with flagging batteries.
Goldman Sachs lost 0.5 percent after saying its fourth-quarter profit would take a $5 billion hit related to the new tax law.
Trading volumes remained light in the holiday week ahead of New Year.
The consumer staples index was the only major gainer, with a 0.5 percent rise.
Altria, Coca-Cola and Philip Morris, gained between 0.9 percent and 1.5 percent.
Amazon slipped 0.6 percent after President Donald Trump targeted the online retailer in a call for the country's postal service to raise prices of shipments in order to recoup costs.
Advancing issues outnumbered decliners on the NYSE by 1,479 to 1,325. On the Nasdaq, 1,510 issues fell and 1,360 advanced. (Reporting by Sruthi Shankar in Bengaluru; Editing by Anil D'Silva)