By Shashwat Chauhan and Kanchana Chakravarty (Reuters) -Wall Street futures fell and Treasury yields rose on Monday after Moody's downgraded the U.S. sovereign rating, sharpening focus on the country's mounting debt.

U.S. stock futures point to a lower open after Moody's stripped the U.S. of its top credit rating. Moodys cut its credit rating on Friday a notch to Aa1 from Aaa due to likely difficulty financng the federal government’s growing budget deficit and the ramifications of rolling over existing U.