Futures fall on weak China data, Ukraine unrest

NEW YORK (Reuters) - U.S. stock index futures fell on Monday on concern China's economy continued to lose momentum and as pro-Russian separatists ambushed Ukrainian forces, escalating a conflict that has kept global markets on tenterhooks recently.

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 the previous month.

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.

Angela Merkel's spokesman said Germany believes a referendum planned by pro-Russian separatists in the eastern city of Donetsk next week would violate Ukraine's constitution and make the situation there even worse.

Pfizer Inc added to the gloomy sentiment as the biggest U.S. drugmaker reported revenues well below analysts' expectations.

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 62 points and Nasdaq 100 e-minis lost 16 points.

Data expected on Monday include ISM's non-manufacturing PMI at 10:00 a.m. EDT.

Occidental Petroleum , the fourth-largest U.S. oil and gas company, reported a 2.6 percent rise in first-quarter profit, helped by higher prices for crude oil and natural gas.

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.

(Reporting by Rodrigo Campos; Editing by Bernadette Baum)