LONDON, Feb 23 : Oil prices reached a six-month high on Monday as the U.S. and Iran prepared for a third round of nuclear talks while increased economic uncertainty was also in focus after the latest U.S. tariff upheaval. Brent crude futures were up 62 cents or nearly 0.9 per cent at $72.38 a barrel, a fresh six-month high, by 1432 GMT while U.S. West Texas Intermediate crude gained 69 cents or 1 per cent to $67.17.  Growing concern over potential military conflict between the U.S. and Iran