* Energy stocks helped by Saudi move to stabilize prices
* Pfizer, Allergan drop after biggest-ever healthcare deal
* Alcoa up as Elliott takes stake
* Indexes up: Dow 0.02 pct, S&P 0.19 pct, Nasdaq 0.28 pct (Updates to early afternoon)
By Abhiram Nandakumar
Nov 23 (Reuters) - U.S. stock indexes held onto meager gains in lackluster early-afternoon trading on Monday in the run-up to Thursday's Thanksgiving holiday.
Energy stocks rose with crude prices after Saudi Arabia agreed to cooperate with other oil producers to stabilize prices.
The S&P energy sector was up 0.8 percent, led by Exxon and Chevron, which rose 0.8 percent and 1.3 percent respectively.
Pfizer's shares were down 2.1 percent at $31.51, after the company said it would buy fellow drugmaker Allergan in a deal valued at about $160 billion, the biggest ever in the healthcare sector.
Allergan fell 2.4 percent to $305.11.
Analysts expressed concerns about what were seen as the low synergies from the deal, its complexity, antitrust issues and a possible delay in Pfizer's plan to split in two companies.
Pfizer and Allergan were the biggest drags on the S&P 500, along with Apple, which was down about 1 percent.
The S&P 500 staged its best performance of the year last week, while the Dow Jones industrial average turned positive for the year.
"We're coming off a very strong performance, a market that has shown tremendous resilience and a strong propensity of 'coming back'," said Andre Bakhos, managing director at Janlyn Capital LLC in Bernardsville, New Jersey.
"Chances are, the bulk of the action will take place Monday and Tuesday and then (traders) will turn their machines off," he said, adding trading was likely to be "very quiet" this week.
At 13:02 p.m. ET (1802 GMT), the Dow Jones industrial average was up 4.45 points, or 0.02 percent, at 17,828.26, the S&P 500 was up 3.87 points, or 0.19 percent, at 2,093.04 and the Nasdaq Composite index was up 14.40 points, or 0.28 percent, at 5,119.32.
Six of the 10 major S&P sectors were higher, underpinned by the 0.8 percent rise in the consumer staples sector.
Tyson Foods jumped 9.8 percent to $47.92 after its quarterly sales beat estimates.
Kellogg rose 4.3 percent to $69.07 after Credit Suisse raised its rating to "outperform".
Alcoa was up 5.2 percent at $9.14. Elliott Management disclosed a 6.5 percent stake in the "undervalued" aluminum maker.
GameStop tumbled 9.2 percent to $35.64 after the video games retailer reported lower quarterly sales and profit.
Mallinckrodt jumped 9.5 percent to $66.81 after the biopharmaceutical company posted a jump in sales.
Advancing issues outnumbered decliners on the NYSE by 1,902 to 1,072. On the Nasdaq, 1,692 issues rose and 1,016 fell.
The S&P 500 index showed 24 new 52-week highs and four new lows, while the Nasdaq recorded 60 new highs and 58 new lows. (Reporting by Abhiram Nandakumar in Bengaluru; Editing by Savio D'Souza and Ted Kerr)