* Pfizer's revenue below expectations
* JPMorgan shares fall premarket on revenue warning
* Futures off: Dow 70 pts, S&P 8 pts, Nasdaq 17 pts (Updates prices, adds Target. B/E Aerospace)
By Rodrigo Campos
NEW YORK, May 5 (Reuters) - U.S. stocks were set to open lower on Monday on concern China's economy is continuing to lose momentum and as pro-Russian separatists ambushed Ukrainian forces, escalating a conflict that has kept global markets on tenterhooks recently.
* Pro-Russian separatists ambushed Ukrainian forces on Monday, triggering heavy fighting on the outskirts of the rebel stronghold of Slaviansk a day after a Ukrainian police station in Odessa was stormed.
* China's manufacturing sector contracted for a fourth consecutive month in April, adding to concerns over the health of the world's second-largest economy. Output and new orders contracted last month, and new export orders slipped back into contraction after a recovery in March.
* Pfizer Inc added to the gloomy sentiment as the biggest U.S. drugmaker reported revenues well below analysts' expectations. Shares fell 1.1 percent in premarket trading.
* S&P 500 e-mini futures fell 8 points and fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract, indicated a lower open. Dow Jones e-minis fell 70 points and Nasdaq 100 e-minis lost 17 points.
* Data expected on Monday include ISM's non-manufacturing PMI at 10:00 a.m. EDT (1400 GMT).
* Target Corp shares fell 1 percent in premarket trading following news that Chief Executive and Chairman Gregg Steinhafel will leave the company in the wake of a devastating data breach late last year that hurt profits, shook customer confidence in the No. 3 U.S. retailer and prompted congressional hearings.
* Occidental Petroleum, the fourth-largest U.S. oil and gas company, reported a better-than-expected profit for the third straight quarter, helped by higher prices for crude oil and natural gas in the United States.
* Shares of JPMorgan Chase fell 2.9 percent in trading before the opening bell. The bank said late on Friday it expects second-quarter revenue from bond and equity trading to decline by about 20 percent from a year earlier.
* German aircraft seating maker Recaro said it was studying the possibility of buying assets from B/E Aerospace after the U.S. company announced a surprise review. B/E Aerospace shares jumped 8.1 percent in premarket trading. (Editing by Bernadette Baum)