LONDON, Jan 30 : Oil prices slipped on Friday on signs that the U.S. may engage in dialogue with Iran over its nuclear programme, reducing concern over potential supply disruptions from a U.S. attack. Brent crude futures were down 21 cents, or 0.3 per cent, at $70.50 a barrel by 1219 GMT. The March contract expires later on Friday. The more active April contract lost 45 cents, or 0.65 per cent, to $69.14. U.S. West Texas Intermediate crude fell 38 cents, or 0.6 per cent, to $65.04 a barrel. "