Brent crude fell by as much as $3 a barrel on Monday, before paring losses, as a breakthrough nuclear deal between world powers and Iran over the weekend led to expectations for an increase in supply. The deal halts Iran's most sensitive nuclear activity and suspends some sanctions by the United States and the European Union on several sectors of Iran's economy for an initial six-month period. Brent was down $1.79 at $109.26 by 1200 GMT, after dropping as low as $108.05 earlier in the session. US oil fell $1.29 to $93.55.