* Weekly jobless claims fall to 265,000
* Pfizer top stock on Dow, S&P
* Nvidia down on Citron Research tweet
* Indexes up: Dow 0.17 pct, S&P 0.17 pct, Nasdaq 0.2 pct (Updates to open)
By Yashaswini Swamynathan
Dec 29 (Reuters) - Strong economic data and gains in healthcare stocks propped up Wall Street on Thursday, a day after the S&P 500 suffered its biggest fall in two months.
A report showed the number of Americans applying for jobless claims fell by 10,000 to 265,000 last week, indicating sustained strength in the labor market.
U.S. equities had been enjoying a rally since the presidential election in November on bets that Donald Trump would introduce tax cuts, deregulation and higher infrastructure spending that would spur economic growth.
The near two-month rally has seen the three main Wall Street indexes rack up double-digit percentage gains, but has left some market participants nervous about a potential correction.
The S&P 500 index suffered its biggest one-day percentage drop on Wednesday, following weak housing data and losses in the technology sector. The triple-digit loss on the Dow pulled it further away from its march towards 20,000.
At 9:38 a.m. ET the Dow Jones industrial average was up 34.26 points, or 0.17 percent, at 19,867.94
The S&P 500 was up 3.98 points, or 0.17 percent, at 2,253.9.
The Nasdaq Composite was up 10.93 points, or 0.2 percent, at 5,449.49.
Nine of the 11 major S&P 500 sectors were higher, led by gains in industrials and utilities.
Nvidia's shares fell 2.5 percent to $106.31, a day after short-seller Citron Research tweeted that the chipmaker's stock could fall to $90 in 2017.
Shares of Advanced Micro Devices, Nvidia's rival, were off 0.7 percent.
Cempra dropped 50 percent to $2.98 after the drug developer said the U.S. Food and Drug Administration rejected its antibiotic treatment for pneumonia.
Advancing issues outnumbered decliners on the NYSE by 1,920 to 635. On the Nasdaq, 1,582 issues rose and 624 fell.
The S&P 500 index showed 1 new 52-week highs and two new lows, while the Nasdaq recorded 28 new highs and 11 new lows. (Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Anil D'Silva)