US STOCKS-Materials, energy stocks weigh on indexes
* 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
* Indexes down: Dow 0.64 pct, S&P 0.79 pct, Nasdaq 0.55 pct (Adds details, changes comment, updates prices)
By Abhiram Nandakumar
Jan 25 (Reuters) - Wall Street looked set to snap a two-day rally on Monday as retreating crude oil prices weighed on materials and energy stocks.
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.
Investors, already rattled by the volatile start to the year and a steep fall in oil prices, are awaiting U.S. GDP data on Friday for a reading on the health of the economy. Continuación...