US STOCKS-Futures down after Saudi air strikes on Yemen
* Oil jumps after air strikes on Yemen
* SanDisk tumbles in premarket after outlook cut
* Weekly jobless claims, flash Markit services sector PMI on tap
* Futures off: Dow 124 pts, S&P 14 pts, Nasdaq 46.25 pts
By Chuck Mikolajczak
NEW YORK, March 26 (Reuters) - U.S. stock index futures were lower on Thursday to put the S&P 500 on track for a fourth straight decline, after Saudi Arabia and its allies launched air strikes on Yemen.
* Oil prices spiked, with Brent crude up 3.4 percent to $58.40 and U.S. crude up 3.5 percent to $50.93 after warplanes from Saudi Arabia and its allies struck Shi'ite Muslim rebels fighting to oust Yemen's president. Halliburton shares gained 1.3 percent to $44.02 in premarket trade.
* U.S. stocks dropped on Wednesday as a slump in technology and biotechs sent the Nasdaq to its biggest decline in nearly a year while the S&P 500 fell through key support levels.
* Semiconductor stocks are likely to be under pressure for a fourth straight session, after SanDisk cut its first-quarter and 2015 revenue outlook and withdrew its other forecasts for the same time frame. Shares of SanDisk tumbled 13 percent to $70.60 before the opening bell. The PHLX semiconductor index had its biggest drop since Oct. 10 on Wednesday and is down 6.3 percent for the week. Continuación...