Japan downgrade, commodity falls hit US futures

U.S. stock index futures fell on Monday, as ratings agency Moody's downgraded Japan's credit rating and commodity prices continued to tumble.

The only major economic data due from the U.S. is the ISM Index for November, expected at 10 a.m.

Earnings of note include online payment service MOL Global's rescheduled results. Its Nasdaq-listed shares tumbled when its CFO resigned only one month after the firm went public.

Earlier in the day, Moody's cut Japan's credit rating to A1 from AA3, shortly after the country's benchmark stock index, the Nikkei 225, closed at a seven-year high. The credit ratings agency cited doubts as to whether Japan could meet its deficit-cutting goals and the timing and effectiveness of its growth-enhancing policy measures.

Meanwhile, U.K.-listed energy stocks fell as Brent crude oil prices continued a five-month losing streak, falling below $70. It comes after OPEC, a group representing the world's biggest oil exporters, announced last week that it would not cut production despite the falling price.

Read MoreGulf stocks rattled by OPEC production put

Miners like Anglo American and Fresnillo also saw falls of more than 4 percent, due to declining silver and gold prices on Monday morning. Precious metals were sent tumbling after Swiss voters rejected proposals to boost the country's gold reserves in a referendum on Sunday.

There was also slower-than-expected growth in China's manufacturing sector. The final reading on HSBC's manufacturing PMI stood at a six-month low of 50.0, while China's official PMI reading of 50.3 was down from 50.8 in October and below expectations of 50.6 in a Reuters poll.

Read MoreWeak factory data spur talk of more PBOC action

Correction: This story has been updated to reflect that MOL Global's chief financial officer resigned last month.