Brent crude declined below a level of $100 a barrel for the first time in nine months amid weaker demand curbed by the signs of slower global economic growth, while West Texas Intermediate dropped to a 4-month low on speculation about rising U.S. supplies. June Brent futures slipped $2.63 to $99.55 on London's ICE and WTI for delivery in May fell $2.65 to $86.06 on the NYMEX.