The BSE benchmark Sensex fell by nearly 31 points in early trade today as funds and investors adopted a cautious approach ahead of RBI policy meeting amid a weak Asian trend.The 30-share barometer fell by 30.86 points, or 0.15 per cent, to 20,072.49 with stocks of oil and gas, consumerdurable and realty trading in the negative.The wide-based National Stock Exchange index Nifty declined by 7 points, or 0.12 per cent, to 6,067.80.In the Asian region, Japan's Nikkei Index fell by 0.68 percent, while Hong Kong's Hang Seng index declined by 0.07 percent in early trade. The US Dow Jones Industrial Average ended 0.10 per cent lower yesterday.