Oil prices dipped for a second consecutive session as concerns about tighter Russian and Iranian supply amid widening Western sanctions checked losses. Both Brent and WTI futures slid after rising for five days in a row last week. Weaker economic data globally and rising supply from non-OPEC countries are also dragging on oil prices. However, worries over tightening Russian and Iranian supply amid sanctions kept a floor under oil prices, with Middle Eastern oil demand increasing.