By Laura Sanicola (Reuters) -Oil prices extended losses on Friday and were heading for a weekly fall as the prospect of increased Iranian oil exports eclipsed fears of potential supply disruption resulting from the Russia-Ukraine crisis. Brent crude futures fell 13 cents, or 0.1%, to $92.84 a barrel by 12:26 p.m. EDT (1526 GMT), extending a 1.9% drop from the previous session. U.S. West Texas Intermediate (WTI) crude futures shed 68 cents, or 0.7%, to $91.08 a barrel after sliding 2% on Thursday. Both benchmark contracts hit their highest levels since September 2014 on Monday, but the prospect…