Oil prices eased about 1% to a one-week low on Tuesday on demand worries following the release of negative economic news from Germany and China, while investors remained cautious ahead of a U.S. Federal Reserve decision on interest rates.Brent futures fell 90 cents, or 1.2%, to $73.01 a barrel by 1:36 p.m. EST (1836 GMT), while U.S. West Texas Intermediate crude slipped 86 cents, or 1.2%, to $69.