Oil prices rose by a dollar a barrel on Tuesday as supply disruptions mounted and traders bet that demand will grow if the US Federal Reserve lowers borrowing costs this week, as is widely expected.Brent crude futures gained 95 cents, or 1.3%, to settle at $73.70 per barrel Both contracts settled at their highest so far this month. US crude futures rose $1.10, or 1.6%, to $71.41.Source: Qatar News Agency