* Alcoa falls after missing earnings estimates
* Amazon shortlists 20 cities for second headquarters
* U.S. jobless claims fall to 45-year low
* Indexes down: Dow 0.3 pct, S&P 0.16 pct, Nasdaq 0.07 pct (Changes comment, adds details, updates prices)
By Sruthi Shankar
Jan 18 (Reuters) - Wall Street's main indexes edged lower on Thursday as declines in healthcare and energy stocks paused a rally that had driven the Dow Jones index to its fastest ever 1,000 point gain.
Merck and Pfizer weighed the most on the S&P healthcare sector, which fell 0.45 percent.
Oil's drop below $69 a barrel on a reported rise in U.S. fuel stocks shaved 0.66 percent off the S&P energy index .
Investors are keeping a close eye on corporate earnings reports, given the runup in stock valuations.
Morgan Stanley wrapped up earnings season for the big U.S. banks with a better-than-expected profit, but its shares were little changed.
"This might just be a little bit of a pullback, especially after yesterday's significant gain, until we get further into the earnings season," said Lindsey Bell, investment strategist at CFRA Research in New York.
However, she said optimism was still intact.
"There is hope and anticipation for progress in policy. Infrastructure will be the next major one, it should help boost economic and corporate activity."
At 10:53 a.m. ET (1553 GMT), the Dow Jones Industrial Average was down 77.54 points, or 0.3 percent, at 26,038.11, the S&P 500 was down 4.39 points, or 0.16 percent, at 2,798.17 and the Nasdaq Composite was down 5.33 points, or 0.07 percent, at 7,292.95.
Economic data in the day was mixed. U.S. homebuilding fell more than expected in December, recording its biggest drop in just over a year, while weekly jobless claims dropped to a 45-year low last week.
Data from China showed its economic growth accelerated for the first time in seven years, putting world stocks on a firm footing.
Republican leaders in the U.S. Congress intensified efforts to pass a temporary extension in funding government operations and avert a shutdown, scheduling a vote on the measure for later Thursday.
The government is operating on its third temporary funding extension since the 2018 fiscal year began on Oct. 1.
Alcoa shares sank 8 percent after the aluminum producer's quarterly earnings missed analysts' estimates.
Amazon said it has short-listed 20 cities, including one in Canada, to build its second headquarters after reviewing 238 proposals and expects to make a decision this year. Its shares rose 0.35 percent.
Bank of New York Mellon fell about 5 percent after the custodian bank said it expected to book more in severance costs in 2018.
Declining issues outnumbered advancers on the NYSE by 2,103 to 727. On the Nasdaq, 1,841 issues fell and 932 advanced. (Reporting by Sruthi Shankar in Bengaluru; Editing by Anil D'Silva)