* Crude oil falls after last week's gains
* Tyco soars after deal to merge with Johnson Controls
* Twitter falls as 4 top executives to leave co
* Futures down: Dow 50 pts, S&P 6.5 pts, Nasdaq 13.5 pts (Adds details, comment, updates prices)
By Abhiram Nandakumar
Jan 25 (Reuters) - U.S. stock indexes were set to open lower on Monday after last week's rally in oil prices lost steam.
Crude prices resumed their slide, after a strong two-day run, as a record output from Iraq flooded a heavily oversupplied market.
U.S. stocks logged their first week of gains in the year last week, with the three indexes closing up 2 percent on Friday.
All eyes will be on the U.S. Federal Reserve's next move on interest rates when the Federal Open Market Committee meets on Jan. 26-27.
Investors, already rattled by the volatile start to the year and a steep fall in oil prices, are also awaiting U.S. GDP data on Friday for a reading on the health of the economy.
"So right now, we're in wait-and-see mode as the market pauses to digest last week's very strong gains," said Adam Sarhan, chief executive of Sarhan Capital in New York.
Corporate results are not likely to improve sentiment, with quarterly profits at S&P 500 companies expected to fall 4.3 percent, according to Thomson Reuters data. Excluding energy companies, earnings are estimated to grow by 1.7 percent.
At 8:28 a.m. ET (1328 GMT), Dow e-minis were down 50 points, or 0.31 percent, with 38,976 contracts changing hands.S&P 500 e-minis were down 6.5 points, or 0.34 percent, with 237,257 contracts traded. Nasdaq 100 e-minis were down 13.5 points, or 0.32 percent, on volume of 46,247 contracts.
Shares of McDonald's were up 3 percent at $121.95 premarket after the Dow component reported better-than-expected same-store sales.
Tyco International jumped 11 percent to $33.95 after Johnson Controls said it would merge with the Irish fire protection and security systems maker. Johnson Controls was down half a percent.
Twitter was down 4.9 percent at $16.99 after Chief Executive Jack Dorsey said four senior executives would leave the social media company.
Caterpillar was down 3.7 percent at $58.71 after Goldman Sachs cut its rating on the stock to "sell".
Halliburton was down 1.6 percent at $29.70 after the oilfield services company reported a 42 percent fall in revenue, while D.R. Horton was up 1 percent at $28, after its profit beat estimates. (Reporting by Abhiram Nandakumar in Bengaluru; Editing by Anil D'Silva)